The operation of a mechanical vending machine as implemented and named by the operation thereof and the information about retrieving the items from the machine. To begin, the stipulation must be made as to the  objective of a mechanical vending machine. This typical process is that a  customer will insert money into the dispenser in order to get the  desired product. The product is delivered from the storage box  within the machine and put where the customer can easily reach and  get the product. The money then resides within the coin box.In addition, since the change is  dropped into the machine, the stipulation must be made as to assets and to  the operation of the machine. By utilizing that method, the mechanical vending machine must  have a coin insert slot for the validation of coins. In addition, there must be an  insert guide for receiving the change. The coin insert handle wholly  represents this ability for the machine to validate the coin. Inside the  housing, there is a handle, which is built of a horizontal bar and  attached to that by a fixed manner, is another handle. The coin slot is  positioned vertically at the adjacent end of the bar, which allows  sufficient length to keep the coin inside the machine. As well, there is a   guide, which guides the coin, to be accepted into the  machine.Having talked about the coin mechanism, the body of the  mechanical vending machine must be stipulated concerning the other  components. The product is delivered on a shelf area in the far end of the  machine. A common element and regarded as the dispensing body. The coin mechanism is  affixed on the body of the machine. To get the product to the  customer there is also a specific part of the machine that calls for the product to be delivered to the  person.Workings of the mechanical vending machine are comprised of:  The product delivery enclosure, whereby the product is stored. Moreover,  the multiple coin mechanisms affixed on the top and most forward parts of  the body. This delivery method should ideally be in the shape of a  box. In the front most part of the machine, a clear window might  be placed to allow many people the ability to see the product inside the mechanical  vending machine. As well, the product is stored within an individual  enclosure, depending on the size and selection of the product, there  numerous places within the enclosure because of the numerous  variety of products offered. When the vend is initiated the product will  be delivered from these compartments to the delivery area.The product falls in a downward movement.  The delivery compartment will be moved in a way that makes the  product activate and fall downwards. The most ideal mechanism behind this is a  piston and a mixture of elastic mechanisms, which are meant to keep the product in  place and deliver the product. These elastics cords act as connection mediums to  the piston and enclosure, supporting the enclosure and implementing  the various storage and delivery mechanisms within the unit. The composition of the cords are elastic due to the condition of the mechanisms.  They are required to be elastic because of the ability for the cord to be pulled  tight and loosened. Overall mass of the product works with gravity and places a vital  importance in the operation of the mechanical vending machine. As things  work on the physics of pulling, pushing and gravity in combination with  the piston.Moreover, this is what happens when a coin is  dropped into the machine. When a coin is placed in the mechanism, the  delivery of the coin guide begins. Thus, by the position of the coin  guide, the coin is placed and guided to appropriate locations. Thus, the coin is  moved to the product enclosure by the handle, which then arrives at the  bridge and enters into the slot. According to this and, the measures, which allow  the product to be delivered, are put in place and the product is  delivered by the act of gravity and additional measures of the  mechanisms involved. After this, the coin enters the box in  which all coins are put for future use.

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Drug resistance is the reduction in effectiveness of a drug in curing a disease or improving a patient’s symptoms. When the drug is not intended to kill or inhibit a pathogen, then the term is equivalent to dosage failure or drug tolerance. More commonly, the term is used in the context of diseases caused by pathogens.Pathogens are said to be drug-resistant when drugs meant to neutralize them have reduced effect. When an organism is resistant to more than one drug, it is said to be multidrug resistant.Drug resistance is an example of evolution in microorganisms. Individuals that are not susceptible to the drug effects are capable of surviving drug treatment, and therefore have greater fitness than susceptible individuals. By the process of natural selection, drug resistant traits are selected for in subsequent offspring, resulting in a population that is drug resistant.Multiple drug resistance or Multidrug resistance is a condition enabling a disease-causing organism to resist distinct drugs or chemicals of a wide variety of structure and function targeted at eradicating the organism. Organisms that display multidrug resistance can be pathologic cells, including bacterial and neoplastic (tumor) cells.Cross-resistance is the tolerance to a usually toxic substance as a result of exposure to a similarly acting substance. It is a phenomenon affecting e.g. pesticides and antibiotics.as an example rifabutin and rifapin cross react in the treatment of tuberculosis. Various microorganisms have survived for thousands of years by their being able to adapt to antimicrobial agents. They do so via spontaneous mutation or by DNA transfer. It is this very process that enables some bacteria to oppose the assault of certain antibiotics, rendering the antibiotics ineffective. These microorganisms employ several mechanisms in attaining multidrug resistance:

Many different bacteria now exhibit multidrug resistance, including staphylococci, enterococci, gonococci, streptococci, salmonella, Mycobacterium tuberculosis and others. In addition, some resistant bacteria are able to transfer copies of DNA that codes for a mechanism of resistance to other bacteria, thereby conferring resistance to their neighbors, which then are also able to pass on the resistant gene.

To limit the development of antibiotic resistance, one should:

It is argued that government legislation will aid in educating the public on the importance of restrictive use of antibiotics, not only for human clinical use but also for treating animals raised for human consumption.

Causes and risk factors

Schematic representation of how antibiotic resistance evolves via natural selection. The top section represents a population of bacteria before exposure to an antibiotic. The middle section shows the population directly after exposure, the phase in which selection took place. The last section shows the distribution of resistance in a new generation of bacteria. The legend indicates the resistance levels of individuals.

Antibiotic resistance can be a result of horizontal gene transfer, and also of unlinked point mutations in the pathogen genome and a rate of about 1 in 108 per chromosomal replication. The antibiotic action against the pathogen can be seen as an environmental pressure; those bacteria which have a mutation allowing them to survive will live on to reproduce. They will then pass this trait to their offspring, which will result in a fully resistant colony.

Several studies have demonstrated that patterns of antibiotic usage greatly affect the number of resistant organisms which develop. Overuse of broad-spectrum antibiotics, such as second- and third-generation cephalosporins, greatly hastens the development of methicillin resistance. Other factors contributing towards resistance include incorrect diagnosis, unnecessary prescriptions, improper use of antibiotics by patients, the impregnation of household items and children’s toys with low levels of antibiotics, and the administration of antibiotics by mouth in livestock for growth promotion. Also unsound practices in the pharmaceutical manufacturing industry can contribute towards the likeliness of creation antibiotic resistant strains. Researchers have recently demonstrated the bacterial protein LexA may play a key role in the acquisition of bacterial mutations.

Drug resistance occurs in several classes of pathogens:

Mechanisms

The four main mechanisms by which microorganisms exhibit resistance to antimicrobials are:

Drug inactivation or modification: e.g. enzymatic deactivation of Penicillin G in some penicillin-resistant bacteria through the production of ?-lactamases. Antibiotic modification is the best known: the resistant bacteria retain the same sensitive target as antibiotic sensitive strains, but the antibiotic is prevented from reaching it. This happens, for example, with  lactamases the  lactamase enzymatically cleaves the four membered  lactam ring, rendering the antibiotic inactive. Over 200 types of  lactamase have been described (table). Most lactamases act to some degree against both penicillins and cephalosporins; others are more specific namely, cephalosporinases (for example, AmpC enzyme found in Enterobacter spp) or penicillinases (for example, Staphylococcus aureus penicillinase).  Lactamases are widespread among many bacterial species (both Gram positive and Gram negative) and exhibit varying degrees of inhibition by lactamase inhibitors, such as clavulanic acid. Alteration of target site: e.g. alteration of PBP—the binding target site of penicillins—in MRSA and other penicillin-resistant bacteria.Alterations in the primary site of action may mean that the antibiotic penetrates the cell and reaches the target site but is unable to inhibit the activity of the target because of structural changes in the molecule. Enterococci are regarded as being inherently resistant to cephalosporins because the enzymes responsible for cell wall synthesis (production of the polymer peptidoglycan) known as penicillin binding proteins have a low affinity for them and therefore are not inhibited. Most strains of Streptococcus pneumoniae are highly susceptible to both penicillins and cephalosporins but can acquire DNA from other bacteria, which changes the enzyme so that they develop a low affinity for penicillins and hence become resistant to inhibition by penicillins. The altered enzyme still synthesises peptidoglycan but it now has a different structure. Mutants of Streptococcus pyogenes that are resistant to penicillin and express altered penicillin binding proteins can be selected in the laboratory, but they have not been seen in patients, possibly because the cell wall can no longer bind the anti-phagocytic M protein. Alteration of metabolic pathway: e.g. some sulfonamide-resistant bacteria do not require para-aminobenzoic acid (PABA), an important precursor for the synthesis of folic acid and nucleic acids in bacteria inhibited by sulfonamides. Instead, like mammalian cells, they turn to utilizing preformed folic acid. Quick Efflux: Active efflux is a mechanism responsible for extrusion of toxic substances and antibiotics outside the cell, this is considered to be a vital part of xenobiotic metabolism. This mechanism is important in medicine as it can contribute to bacterial antibiotic resistance.Efflux systems function via an energy-dependent mechanism (Active transport) to pump out unwanted toxic substances through specific efflux pumps. Some efflux systems are drug-specific while others may accommodate multiple drugs, and thus contribute to bacterial multidrug resistance (MDR).

There are three known mechanisms of fluoroquinolone resistance. Some types of efflux pumps can act to decrease intracellular quinolone concentration. In gram-negative bacteria, plasmid-mediated resistance genes produce proteins that can bind to DNA gyrase, protecting it from the action of quinolones. Finally, mutations at key sites in DNA gyrase or Topoisomerase IV can decrease their binding affinity to quinolones, decreasing the drug’s effectiveness.

Bacterial efflux pumps are proteinaceous transporters localized in the cytoplasmic membrane of all kinds of cells. They are active transporters meaning that they require a source of chemical energy to perform their function. Some are primary active transporters utilizing Adenosine triphosphate hydrolysis as a source of energy, while others are secondary active transporters (uniporters, symporters or antiporters) in which transport is coupled to an electrochemical potential difference created by pumping out hydrogen or sodium ions outside the cell.Bacterial efflux transporters are classified into five major superfamilies, based on the amino acid sequence and the energy source used to export their substrates:

Of these only the ABC superfamily are primary transporters, the rest being secondary transporters utilizing proton or sodium gradient as a source of energy. While MFS dominates in Gram positive bacteria , the RND family is unique to Gram-negatives.

In the case of imipenem resistant Pseudomonas aeruginosa, lack of the specific D2 porin confers resistance, as imipenem cannot penetrate the cell. This mechanism is also seen with low level resistance to fluoroquinolones and aminoglycosides. Increased efflux via an energy-requiring transport pump is a well recognised mechanism for resistance to tetracyclines and is encoded by a wide range of related genes, such as tet(A), that have become distributed in the enterobacteriaceae.

Function

Although antibiotics are the most clinically important substrates of efflux systems, it is probable that most efflux pumps have other natural physiological functions. Examples include:

The ability of efflux systems to recognize a large number of compounds other than their natural substrates is probably because substrate recognition is based on physicochemical properties, such as hydrophobicity, aromaticity and ionizable character rather than on defined chemical properties, as in classical enzyme-substrate or ligand-receptor recognition. Because most antibiotics are amphiphilic molecules – possessing both hydrophilic and hydrophobic characters, they are easily recognized by many efflux pumps.

Impact on antimicrobial resistance

The impact of efflux mechanisms on antimicrobial resistance is large, this is usually attributed to the following:

Molecular epidemiology of resistance genes

Resistance in bacteria can be intrinsic or acquired. Intrinsic resistance is a naturally occurring trait arising from the biology of the organism for example, vancomycin resistance in Escherichia coli. Acquired resistance occurs when a bacterium that has been sensitive to antibiotics develops resistance this may happen by mutation or by acquisition of new DNA.

Mutation is a spontaneous event that occurs regardless of whether antibiotic is present. A bacterium carrying such a mutation is at a huge advantage as the susceptible cells are rapidly killed by the antibiotic, leaving a resistant subpopulation. Transferable resistance was recognised in 1959, when resistance genes found in shigella transferred to E coli via plasmids. Plasmids are self replicating circular pieces of DNA, smaller than the bacterial genome, which encode their transfer by replication into another bacterial strain or species. They can carry and transfer multiple resistance genes, which may be located on a section of DNA capable of transfer from one plasmid to another or to the genome a transposon (or “jumping gene”). Because the range of bacteria to which plasmids can spread is often limited, transposons are important in spreading resistance genes across such boundaries. The mecA gene found in MRSA may well have been acquired by transposition.Plasmid evolution can be complex, but modern molecular techniques can give an understanding (as is the case with the plasmids that contain the tetM gene and are found throughout the world in Neisseria gonorrhoeae).

Bacteriophages (viruses that infect bacteria) can also transfer resistance, and this is frequently seen in staphylococci. When bacteria die they release DNA, which can be taken up by competent bacteria a process known as transformation. This process is increasingly recognised as important in the environment and is probably the main route for the spread of penicillin resistance in Streptococcus pneumoniae, by creation of “mosaic penicillin binding protein genes.

Origins of resistance genes

The origins of antibiotic resistance genes are obscure because at the time that antibiotics were introduced the biochemical and molecular basis of resistance was yet to be discovered. Bacteria collected between 1914 and 1950 (the Murray collection) were later found to be completely sensitive to antibiotics. They did, however, contain a range of plasmids capable of conjugative transfer None of the Murray strains was resistant to sulphonamides, although these had been introduced in the mid-1930s; resistance was reported in the early 1940s in streptococci and gonococci. The introduction of streptomycin for treating tuberculosis was thwarted by the rapid development of resistance by mutation of the target genes. Mutation is now recognised as the commonest mechanism of resistance development in Mycobacterium tuberculosis, and the molecular nature of the mutations conferring resistance to most antituberculosis drugs is now known. Favourable mutations that arise in bacteria can be mobilised via insertion sequences and transposons on to plasmids and then transferred to different bacterial species.

In considering the evolution and dissemination of antibiotic resistance genes it is important to appreciate the rapidity of bacterial multiplication and the continual exchange of bacteria among animal, human, and agricultural hosts throughout the world. There is support for the notion that determinants of antibiotic resistance were not derived from the currently observed bacterial host in which the resistance plasmid is seen. DNA sequencing studies of  lactamases and aminoglycoside inactivating enzymes show that despite similarities within the protein studies of the two families, there are substantial sequence differences.  As the evolutionary time frame has to be less than 50 years it is not possible to derive a model in which evolution could have occurred by mutation alone from common ancestral genes. They must have been derived from a large and diverse gene pool presumably already occurring in environmental bacteria. Many bacteria and fungi that produce antibiotics possess resistance determinants that are similar to those found in clinical bacteria.Gene exchange might occur in soil or, more likely, in the gut of humans or animals. It has been discovered that commercial antibiotic preparations contain DNA from the producing organism, and antibiotic resistance gene sequences can be identified by the polymerase chain reaction.

Genes either exist in nature already or can emerge by mutation rapidly. Rapid mutation has been seen with (a) the TEM  lactamase, resulting in an extension of the substrate profile to include third generation cephalosporins (first reported in Athens in 1963, one year after the introduction of ampicillin) and (b) the IMI-1 lactamase (reported from a Californian hospital before imipenem was approved for use in the United States).The selection pressure is heavy, and injudicious use of antibiotics, largely in medical practice, is probably responsible although agricultural and veterinary use contributes to resistance in human pathogens. The addition of antibiotics to animal feed or water, either for growth promotion or, more significantly, for mass treatment or prophylaxis (or both treatment and prophylaxis) in factory farmed animals, is having an unquantified effect on resistance levels.Bacteria clearly have a wondrous array of biochemical and genetic systems for ensuring the evolution and dissemination of antibiotic resistance.

1.    ß-lactam resistance

ß-lactams belong to a family of antibiotics which is characterized by a ß-lactam ring. Penicillins, cephalosporins, clavams (or oxapenams), cephamycins and carbapenems are members of this family. The integrity of the ß-lactam ring is necessary for the activity which results in the inactivation of a set of transpeptidases that catalyze the final cross-linking reactions of peptidoglycan synthesis. Resistance to ß-lactams in clinical isolates is primarily due to the hydrolysis of the antibiotic by a ß-lactamase. Mutational events resulting in the modification of PBPs (penicillin binding proteins) or cellular permeability can also lead to ß-lactam resistance. ß-lactamases constitute a heterogenous group of enzymes. Several classification schemes have been proposed according to their hydrolytic spectrum, susceptibility to inhibitors, genetic localisation (plasmidic or chromosomal), gene or amino-acid protein sequence. The functional classification scheme of ß-lactamases proposed by Bush, Jacoby and Medeiros (1995) defines four groups according to their substrate and inhibitor profiles. Group 1 are cephalosporinases that are not well inhibited by clavulanic acid; group 2 penicillinases, cephalosporinases, and broad-spectrum ß-lactamases that are generally inhibited by active site-directed ß-lactamase inhibitors; group 3 metallo-ß-lactamases that hydrolyze penicillins, cephalosporins, and carbapenems and that are poorly inhibited by almost all ß-lactam-containing molecules; group 4 penicillinases that are not well inhibited by clavulanic acid. Subgroups were also defined according to rates of hydrolysis of carbenicillin or cloxacillin (oxacillin) by group 2 penicillinases. The classification initially introduced by Ambler (1980) and based on the amino-acid sequence recognizes four molecular classes designated A to D. Classes A, C, and D gather evolutionarily distinct groups of serine enzymes, and class B the zinc-dependent (”EDTA-inhibited”) enzymes. Fig : ß-lactamases

The bla gene encoding the TEM-1 ß-lactamase is the most encountered AmpR marker used in molecular biology (pBR and pUC plasmids). TEM-1 is a widespread plasmidic ß-lactamase that attacks narrow-spectrum cephalosporins, cefamandole, and cefoperazone and all the anti-gram-negative-bacterium penicillins except temocillin. Aminothiazol chephalosporins, cephamycins, monobactams and carbapenems are resistant to its action. It belongs to the Bush-Jacoby-Medeiros group 2b and the molecular class A. The TEM-1 enzyme was first reported from an E. coli isolate in 1965 and is now the commonest ß-lactamase found in enterobacteriaceae. Resistance in more than 50% of AmpR E. coli clinical isolates is due to TEM-1. Most extended-spectrum ß-lactamases (ESBLs) derive from TEM-1, TEM-2 and SHV-1 by mutations generating 1- to 4-amino-acid sequence substitutions.

2.    Aminoglycoside resistance

Aminoglycosides (Streptomycin, kanamycin, tobramycin, amikacin,…) are compounds that are characterized by the presense of an aminocyclitol ring linked to aminosugars in their structure. Their bactericidal activity is attributed to the irreversible binding to the ribosomes although their interaction with other cellular structures and metabolic processes has also been considered. They have a broad antimicrobial spectrum. They are active against aerobic and facultative aerobic Gram-negative bacilli and some Gram-positive bacteria of which staphylococci. Aminoglycosides are not active against anaerobes and rikettsia. Spectinomycin which is an aminocyclitol devoided of aminosugars is by extension included in the familiy of aminoglycosides. It also differs from them by its bacteriostatic ativity and by its way of action. Spectinomycin acts on protein synthesis during the mRNA-ribosome interaction and it does not lead to mistranslation like aminoglycosides do. Three mechanisms of resistance have been recognized, namely ribosome alteration, decreased permeability, and inactivation of the drugs by aminoglycoside modifying enzymes. The latter mechanism is of most clinical importance since the genes encoding aminoglycoside modifying enzymes can be disseminated by plasmids or transposons.

Ribosome alteration

High level resistance to streptomycin and spectinomycin can result from single step mutations in chromosomal genes encoding ribosomal proteins: rpsL (or strA), rpsD (or ramA or sud2), rpsE (eps or spc or spcA). Mutations in strC (or strB) generate a low-level streptomycin resistance.

Decreased permeability Absence of or alteration in the aminoglycoside transport system, inadequate membrane potential, modification in the LPS (lipopolysacchaccarides) phenotype can result in a cross resistance to all aminoglycosides.Inactivation of aminoglycosides These enzymes are classified into three major classes according to the type modification: AAC (acetyltransferases), ANT (nucleotidyltransferases or adenyltransferases), APH (phosphotransferases). This classification was extensively reviewed by Shaw et al. (1993).

ant(3”)-Ia (synonyms: aadA, aad(3”)(9))confers resistance to streptomycin and spectinomycin. The gene has been found in association with several transposons (Tn7, Tn21, …) and is ubiquitous among gram-negative bacteria.aph(3′)-II (synonyms: aphA-2, nptII) confers resistance to Km (Kanamycin), Neo (Neomycin), Prm (Paromomycin), Rsm (Ribostamycin), But (Butirosin), GmB (GentamycinB). This gene is rarely found in clinical isolates. aph(3′)-II is associated with transposon Tn5 and observed in gram-negative bacteria and Pseudomonas sp. However, its relative abundance in environmental KanR isolates seems to be low (Recorbet et al., 1992; Leff et al., 1993; Smalla et al., 1993).aph(3′)-III (synonyms: nptIII) confers resistance to Km (Kanamycin), Neo (Neomycin), Prm (Paromomycin), Rsm (Ribostamycin), Lvdm (Lividomycin), But (Butirosin), GmB (GentamycinB). Amk (Amikacin) and Isp (Isepamicin) are also modified in vitro, but according to the susceptibility standards established by NCCLS resistance is only expressed at a low level by many strains. aph(3′)-III is commonly distributed among gram-positive bacteria but has also been observed in Campylobacter spp.

nptIII is not frequent in molecular biology but can be found on some Agrobacterium vectors for plant transformation (Bevan, 1984).

3.    Tetracycline resistance

Tetracyclines (tetracycline, doxycycline, minocycline, oxtetracycline) are antibiotics which inhibit the bacterial growth by stopping protein synthesis. They have been widely used for the past forty years as therapeutic agent in human and veterinary medicine but also as growth promotor in animal husbandry. The emergence of bacterial resistances to these antibiotics has nowadays limited their use. Three different specific mechanisms of tetracycline resistance have been identified so far: tetracycline efflux, ribosome protection and tetracycline modification. Tetracycline efflux is achieved by an export protein from the major facilitator superfamily (MFS). The export protein was shown to function as an electroneutral antiport system which catalyzes the exchange of tetracycline-divalent-metal-cation complex for a proton. In Gram-negative bacteria the export protein contains 12 TMS (transmembrane fragments) whereas in Gram-positive bacteria it displays 14 TMS. Ribosome protection is mediated by a soluble protein which shares homolgy with the GTPases participating in protein synthesis, namely EF-Tu and EF-G. The third mechanism involves a cytoplasmic protein that chemically modifies tetracycline. This reaction takes only place in the presence of oxygen and NADPH and does not function in the natural host (Bacteroides). The two first mechanisms are the most widespread and most of their genes are normally acquired via transferable plasmids and/or transposons. These two mechanisms were observed both in aerobic and anaerobic Gram-negative or Gram-positive bacteria demonstrating their wide distribution among the bacterial kingdom. To date, about sixty-one tetracycline resistance genes have been sequenced and thirty-two classes of genes identified in non-producers and producers (Streptomyces). Each new class is identified by its inability to hybridize with any of the known tet genes under stringent conditions. A new nomenclature for the resistance determinants has been proposed for the future with the S. B. Levy group to coordinate the naming of the

Several tetracycline resistance determinants are currently used in molecular biology. The most encountered are the tetA genes of classes A (RP1, RP4 or Tn1721 derivatives), B (Tn10 derivatives) and C (pSC101 or pBR322 derivatives) encoding a tetracycline efflux system. These genes are regulated by a repressor protein (TetR). This feature has also been exploited to construct tightly regulated, high level mammalian expression systems by using the regulatory elements of the Tn10 tetracycline operon (Tet-OffTM and Tet-OnTM Expression Systems & Cell Lines,Clontech).The tetM gene from Tn916 which can be expressed both in Gram-positive and Gram-negative bacteria is also frequently used. Several Bacteroides/Escherichia shuttle vectors contain the tetQ gene. tetM and tetQ encode a soluble protein protecting the ribosome from the inhibiting effects of tetracycline. The distribution of these genes is given in the pages relating to the determinant classification.

Some Resistant pathogens

Staphylococcus aureus:

Staphylococcus aureus (colloquially known as “Staph aureus” or a Staph infection) is one of the major resistant pathogens. Found on the mucous membranes and the skin of around a third of the population, it is extremely adaptable to antibiotic pressure. It was the first bacterium in which penicillin resistance was found—in 1947, just four years after the drug started being mass-produced. Methicillin was then the antibiotic of choice, but has since been replaced by oxacillin due to significant kidney toxicity. MRSA (methicillin-resistant Staphylococcus aureus) was first detected in Britain in 1961 and is now “quite common” in hospitals. MRSA was responsible for 37% of fatal cases of blood poisoning in the UK in 1999, up from 4% in 1991. Half of all S. aureus infections in the US are resistant to penicillin, methicillin, tetracycline and erythromycin.

Methicillin Resistant Staphylococcus Aureus (MRSA) is acknowledged to be a human commensal and pathogen. MRSA has been found in cats, dogs and horses, where it can cause the same problems as it does in humans. Owners can transfer the organism to their pets and vice-versa, and MRSA in animals is generally believed to be derived from humans.

This left vancomycin as the only effective agent available at the time. However, strains with intermediate (4-8 ug/ml) levels of resistance, termed GISA (glycopeptide intermediate Staphylococcus aureus) or VISA (vancomycin intermediate Staphylococcus aureus), began appearing in the late 1990s. The first identified case was in Japan in 1996, and strains have since been found in hospitals in England, France and the US. The first documented strain with complete (>16 ug/ml) resistance to vancomycin, termed VRSA (Vancomycin-resistant Staphylococcus aureus) appeared in the United States in 2002.

A new class of antibiotics, oxazolidinones, became available in the 1990s, and the first commercially available oxazolidinone, linezolid, is comparable to vancomycin in effectiveness against MRSA. Linezolid-resistance in Staphylococcus aureus was reported in 2003.

CA-MRSA (Community-acquired MRSA) has now emerged as an epidemic that is responsible for rapidly progressive, fatal diseases including necrotizing pneumonia, severe sepsis and necrotizing fasciitis. Methicillin-resistant Staphylococcus aureus (MRSA) is the most frequently identified antimicrobial drug-resistant pathogen in US hospitals. The epidemiology of infections caused by MRSA is rapidly changing. In the past 10 years, infections caused by this organism have emerged in the community. The 2 MRSA clones in the United States most closely associated with community outbreaks, USA400 (MW2 strain, ST1 lineage) and USA300, often contain Panton-Valentine leukocidin (PVL) genes and, more frequently, have been associated with skin and soft tissue infections. Outbreaks of community-associated (CA)-MRSA infections have been reported in correctional facilities, among athletic teams, among military recruits, in newborn nurseries, and among active homosexual men. CA-MRSA infections now appear to be endemic in many urban regions and cause most CA-S. aureus infections.

Streptococcus and Enterococcus

Streptococcus pyogenes (Group A Streptococcus: GAS) infections can usually be treated with many different antibiotics. Early treatment may reduce the risk of death from invasive group A streptococcal disease. However, even the best medical care does not prevent death in every case. For those with very severe illness, supportive care in an intensive care unit may be needed. For persons with necrotizing fasciitis, surgery often is needed to remove damaged tissue. Strains of S. pyogenes resistant to macrolide antibiotics have emerged, however all strains remain uniformly sensitive to penicillin.

Resistance of Streptococcus pneumoniae to penicillin and other beta-lactams is increasing worldwide. The major mechanism of resistance involves the introduction of mutations in genes encoding penicillin-binding proteins. Selective pressure is thought to play an important role, and use of beta-lactam antibiotics has been implicated as a risk factor for infection and colonization. Streptococcus pneumoniae is responsible for pneumonia, bacteremia, otitis media, meningitis, sinusitis, peritonitis and arthritis.

Penicillin-resistant pneumonia caused by Streptococcus pneumoniae (commonly known as pneumococcus), was first detected in 1967, as was penicillin-resistant gonorrhea. Resistance to penicillin substitutes is also known as beyond S. aureus. By 1993 Escherichia coli was resistant to five fluoroquinolone variants. Mycobacterium tuberculosis is commonly resistant to isoniazid and rifampin and sometimes universally resistant to the common treatments. Other pathogens showing some resistance include Salmonella, Campylobacter, and Streptococci.

Enterococcus faecium is another superbug found in hospitals. Penicillin-Resistant Enterococcus was seen in 1983, vancomycin-resistant enterococcus (VRE) in 1987, and Linezolid-Resistant Enterococcus (LRE) in the late 1990s.

Pseudomonas aeruginosa

Pseudomonas aeruginosa is a highly prelevant opportunistic pathogen. One of the most worrisome characteristics of P. aeruginosa consists in its low antibiotic susceptibility. This low susceptibility is attributable to a concerted action of multidrug efflux pumps with chromosomally-encoded antibiotic resistance genes (e.g. mexAB-oprM, mexXY etc) and the low permeability of the bacterial cellular envelopes. Besides intrinsic resistance, P. aeruginosa easily develop acquired resistance either by mutation in chromosomally-encoded genes, or by the horizontal gene transfer of antibiotic resistance determinants. Development of multidrug resistance by P. aeruginosa isolates requires several different genetic events that include acquisition of different mutations and/or horizontal transfer of antibiotic resistance genes. Hypermutation favours the selection of mutation-driven antibiotic resistance in P. aeruginosa strains producing chronic infections, whereas the clustering of several different antibiotic resistance genes in integrons favours the concerted acquisition of antibiotic resistance determinants. Some recent studies have shown that phenotypic resistance associated to biofilm formation or to the emergence of small-colony-variants may be important in the response of P. aeruginosa populations to antibiotics treatment.

Clostridium difficile

Clostridium difficile is a nosocomial pathogen that causes diarrheal disease in hospitals worldwide. Clindamycin-resistant C. difficile was reported as the causative agent of large outbreaks of diarrheal disease in hospitals in New York, Arizona, Florida and Massachusetts between 1989 and 1992. Geographically dispersed outbreaks of C. difficile strains resistant to fluoroquinolone antibiotics, such as Cipro (ciprofloxacin) and Levaquin (levofloxacin), were also reported in North America in 2005.

Salmonella and E. coli

E. coli and Salmonella come directly from contaminated food. Of the meat that is contaminated with E. coli, eighty percent of the bacteria are resistant to one or more drugs made; it causes bladder infections that are resistant to antibiotics (“HSUS Fact Sheet”). Salmonella was first found in humans in the 1970s and in some cases is resistant to as many as nine different antibiotics (“HSUS Fact Sheet”). When both bacterium are spread, serious health conditions arise. Many people are hospitalized each year after becoming infected, and some die as a result.

Acinetobacter baumannii

On the 5th November 2004, the Centers for Disease Control and Prevention (CDC) reported an increasing number of Acinetobacter baumannii bloodstream infections in patients at military medical facilities in which service members injured in the Iraq/Kuwait region during Operation Iraqi Freedom and in Afghanistan during Operation Enduring Freedom were treated. Most of these showed multidrug resistance (MRAB), with a few isolates resistant to all drugs tested.

Summary:

We frequently refer to bacteria as being resistant to antibiotics, but rarely do we consider what that means. Even the most resistant bacterium can be inhibited or killed by a sufficiently high concentration of antibiotic; patients, however, would not be able to tolerate the high concentration required in some cases. Bacterial species vary tremendously in their susceptibility to an antibiotic for example, most strains of Streptococcus pneumoniae in Britain are inhibited by 0.01 mg/l of benzyl penicillin (the minimum inhibitory concentration), whereas for Escherichia coli 32-64 mg/l are required to inhibit growth, a level which cannot be achieved in the human body. This introduces the concept of clinical resistance, which is dependent on outcome and is all too often ignored. Clinical resistance is a complex concept in which the type of infecting bacterium, its location in the body, the distribution of the antibiotic in the body and its concentration at the site of infection, and the immune status of the patient all interact.

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Secure Authentication Mechanism in Mobile Internet Protocol Version 6

 

Mojtaba Sadeghi, Hamid Reza Naji, Tawfik Zeki

Department of Computer Engineering

Islamic Azad University

Dubai ,UAE

                                                            June 2009

  

Abstract

This paper  presents a secure authentication method  for Mobile IPv6. As a default IPsec is used for secure signaling messages between the Mobile Node and other agents in Mobile IPv6 networks. Mobile IPv6 message transactions include the Binding Updates and Acknowledgement messages as well. We propose a new mechanism for securing Mobile IPv6 signaling between Mobile Node and other agents.  The proposed method consists a Mobile IPv6 message authentication option and cookie management that can be added to the current protocols for securing IPV6. Also we investigate an architecture to integrate the mobility authentication signaling. This architecture is implemented and evaluated. In Mobile IPV4 protocol and also some authentication protocols of Mobile IPV6, there are some difficulties for satisfying timing requirements. We show the latency can be decrease between the Mobile IPV6 node, Home Agent and Correspondent Node with creating a cookie file keeping the mobile node identification.

 

1.Introduction

The security of a mechanism and protocol depends on the reliability and infrastructure of the Internet routing. The protocol will work between mobile nodes and any other Internet node that have no previous connection or relation with, and also we assume there is not any specific global security infrastructure. When Mobile IPV6 was developed, the built-in technology made it possible for users to change their points of attachment to the Internet while they still using the same IP connections established before. But, authentication and authorization, which are too important functions in wireless networks, were not considered during the design and creation. Therefore, this paper investigates the integration of MIPv6 and Authentication systems and develops integrated architectures as well. The mechanism described in this paper is a simplified version of the actual Mobile IPV6 protocol. We focus on the binding-update messages sent by the mobile node to its correspondents. In fact authentication service is the most important protection and inspection services in wireless networking. Security designing in mobile network is a critical stage in developing and establishing a Network infrastructure system. While a wireless system provides economic, convenience and efficient network , it must also be secured to prevent attack for theft and damage of data and  information . A safe and secure wireless network can ensure that your data transmissions are not intercepted, abuse, misuse by unknown third-party. Unsecured wireless networks are vulnerable to many types of problems, including:

-Theft of information

-Corruption or illegal modification of data

-Interception of interaction ,transaction and communication

-Insider abusing of network data and resources

Establishing a professional and secure wireless network means implementing a framework of authentication, encryption and key management protocols[1]. We focus on authentication with IPV6  in this paper. As a description , authentication is a process of verifying that a device or user that is attempting to log in to the wireless network, should be allowed on the network. Encryption and Key Management are processes and techniques that are make more complex and scramble data so that an unauthorized user or device that receives the data cannot use that.

 

2. IPv6 Review

Based on the recent concerns over the lack of internet addresses and the desire to provide more functionality for modern mobile devices, an upgrade of the old and current version of the Internet   Protocol (IP), called IPv4, has been established. This new version, called IP version 6 (IPv6), resolves  weakness of IPv4 design issues and made a revolution in Internet in recent years. The long of addresses in IPv6 are 128 bits. The first 64 bit are used for the link prefix. Which it  is assigned to every link and gets advertised through routers on that link. The second 64 bit of the address belongs to the interface  identifier .There are different scopes of IPv6 addresses in networking. The different scopes can be     diagnostic by looking at certain bit patterns of the address prefix.  

We can call the most important scopes in IPv6 as below:

- Link local: An address with a scope of link local only can be used to communicate within the node’s link. Packets with this link addresses will not be

routed outside the link. The first 64 bits of this addresses are fixed and look likes this: 1111111010 0 . . – Site local

First 10 bits Proceeding 54 bits. Link local addresses are like unique addresses  inside a site. The size of a site will define by site administrator. It can be a small home network with two or three clients or even the network of a university with hundreds nodes. The first 64 bits of site local addresses look like follows: 1111111011 0 . . . – Subnet ID

The 16 subnet bits are used to differentiate sites and First 10 bits Proceeding 38 bits last 16 bits. Protocol transitions are not easy and the transition from IPv4 to IPv6 is no exception. Protocol transitions are typically deployed by installing and configuring the new protocol on all nodes within the network and verifying that all node and router operations work successfully. Although this might be possible in a small or medium sized organization, the challenge of making a rapid protocol transition in a large organization is very difficult. Additionally, given the scope of the Internet, rapid protocol transition from IPv4 to IPv6 is an impossible issue. The designers of IPv6 recognize that the transition from IPv4 to IPv6 will take years and that there might be organizations or hosts within organizations that will continue to use IPv4 indefinitely[1]. IPv6 solves the network address limitations of  the current IPv4 protocol by replacing IPv4’s  32-bit addresses with 128-bit addresses. Different elements were considered during the design of IPv6. One of this consideration is forecasting about the needs of future markets. We can guess that future of internet markets would rely on more security, high efficiency, and mobility[7]. Another successful issue of IPv6 designing is the way of internet’s transition from IPv4. This kind of transition involves with different software, hardware, protocol and infrastructure problems. Fortunately IPv6 has been developed to work with IPV4 network protocol as well. By creating a tunnel to transfer IPv6 packets or by creating a tunnel for transferring other protocol packets, IPv6 will support without requiring any fundamental changes. When a mobile node is far from it’s home agent, it sends information about its current location to the home agent. Any node that it wants to start interaction and communication with a mobile node will use the home address of the mobile node for this communication and sending packets. The home agent intercepts these packets information, and via using tunnels the packets to the mobile node’s care-of address. In fact Mobile Network IPv6 uses care-of address .But for supporting route optimization for direct connection between Mobile Node and Correspondent Node, the Correspondent node will use IPv6 header than the IP encapsulation. Mobile IPv6 technology allows a Mobile Node to move within the Internet infrastructure without loosing an old established connection. It means for a Mobile Node to be reachable at any time by a Correspondent Node it must have an address that not change. In fact this address belongs to the subnet of home network. In Mobile IPv6 this address is called, Home Address or HoA. If Mobile Node be available in its home network, all packets that want to reach to it, can reach the through the normal routing way. In this situation the Home Agent is topologically correct for the Mobile Node. But if the Mobile Node moves to another subnet, it must to update a Care of Address that topologically this address belongs to the new network. From now Mobile Node  will not be reachable through its HoA as well. Home Agent is responsible to receive all packets that destined to the Mobile Node, whenever Mobile Node is in another visited network. Whenever Home agent receives a packet, it would establish a tunnel it to the Mobile Node’s current Care of Address. It proves the Mobile Node has to update its Home Agent about its current Care of Address regular. It means Home Agent will forward any packets destined to the Mobile Node’s Home Address, to its current Care of Address in visited network. These packets will send through a tunnel to the Mobile Node. It should be considered that the tunnel begins from the Home Agent and will end at the Mobile Node. Mobile IPv6 works like transparent for upper layers like applications. Any time Mobile Node wants to send a packet to the Correspondent Node, it can send it direct to it’s address.

 

3. Security on Mobile IPV6

 3.1. Data Encryption and authentication protocol

One of the solution for making sure that unauthorized users or systems do not access on your wireless and mobile network is to encrypt your data and files. The famous and basic encryption method, WEP (wired equivalent privacy), unfortunately was found to be completely weak and nonstable. WEP works on a shared key technology, or password, to prevent unauthorized access. Anyone who find the WEP key or even stronger key can join and misuse the wireless network. There is no any mechanism or technique in WEP  to automatically change this key, and some tools have produced that can crack a WEP key very fast , even less that 60 sec! It means it will not take long time for an attacker to access a WEP-encrypted in wireless network. We can say the procedure of  RADIUS server is receiving end user requests, then authenticating the user, and finally providing the NAS plus all of the  information for it to deliver services. This protocol of authentication provides a centralized security system to control access to the network resources. Lightweight Directory Access Protocol or LDAP  is called another authentication protocol which defines organized and accessed information. As we know an authentication protocol is a set of rules for communication between server and clients. By implementing LDAP, Network administrator can control users and clients easier with centralize and secure user information[12]. Also there are other mechanisms for mobile authenticating clients, the combination of  RADIUS, EAP, and LDAP is the most common and available solution in use in business today.  Each component has associated open-source software that is freely available for network administrators to download, configure, and use. Thus, with the hardware in place, installation of an authentication system is inexpensive[15]. 

 

3.2. Hijacking and Spoofing on Mobile IPV6 Networks

The first difficulty of IP networks is that it is difficult to know where information really comes from. An attack called IP spoofing takes advantage of this weakness. Since the source IP address of a packet has no influence to the deliverability, it can easily be changed. The attack – called spoofing – makes a packet coming from one machine appear to come from somewhere else altogether. It’s obvious that IP based address is not trustable at all, because everyone can claims he is the owner of this IP address. Even after authentication step , still everything is not safe against sessions hijacking. It means after identification of a person, we can not make sure he will be the same person during the rest of that session. That’s why all source of data must authenticated during the transmission. Still most of networks in the world are based on Ethernet or cabling LANs. This type of network normally are cheap, globally available, easy understood and fast to expand. But making spying is easy in these networks, because any node is able to read every transmitted packet over the LAN. Formally, each network card only listens and responds to the packets that specifically belongs to it, but it is not difficult to ask these devices to listen all packets during passing on the wire. The first recommendation for all Mobile IP networks is to use encryption and authentication the data. But there are still problems on that. We should consider all encryption keys will be exchanged during communicating parties. It’s a rule that encryption keys use encryption algorithms to encrypt and decrypt data. 

 

3.3. Mobile Node MAC address and Authentication

A sorted care-of address is a care-of address that obtained by mobile node as a local IP address. This IP address will be dynamically acquire, may be through a DHCP server or via a foreign agent. After assigning a routable IP address to MN, the mobile node is now able to establish and communicate directly with it’s home agent, careless of  foreign agent. By implementing of this method, mobility decapsulation has done. Sometimes Mobile Node uses the Mobile Node Identifier option to establish of communication and enable the Home Agent to start using of available authentication infrastructure. One of the most difficult step for an attacker is finding the MAC Address of wireless Lan[7]. Many of systems may trust on a faked MAC address, as an authorized wireless router or client. Attacker can start denial of service attacks by passing access control mechanisms in wireless. MAC addresses have been used as unique layer 2 for network identifier in Mobile IPV6 Networks. As we know MAC address is unique in the world for all network-based devices. Organizationally unique identifiers (OUI) has allocated to all hardware manufacturers specially network products manufacture. Generally the MAC address of a client or mobile node is used as an authentication parameter or a unique identifier for making security in authentication level. When an attacker changes their MAC address they continue to utilize the wireless card for its intended layer 2 transport purpose, transmitting and receiving from the same source MAC. All 802.11 network protocol use their MAC addresses to be changed, with support from the manufacturer[6]. Linux users can change their MAC address with some command or programming with C program. But windows users are able to change  their MAC address by configuring the properties of lan card drivers. We should care that an attacker may choose to change the MAC address for different  reasons[15]. The Mobile IPv6 protocol enables a Mobile Node to move from one network to another network without the need to change its old IPv6 address. Because a Mobile Node is always routable and addressable by its home agent, which is the Mobile Node’s IPv6 address. When a Mobile Node is far from its home network, messages can be routed to it using the Mobile Node’s home address. Normally the movement of a mobile node is completely invisible to transport and other layer protocols. 

 

3.4. Mobile IPV6 Accounting

Mobile IPV6 accounting can be divided to four processes: metering, pricing, charging and billing. Actually the duty of metering process would be measure and collects the resource usage information which is related to a single customer’ service. Also the task of pricing would be the process of determining a cost per unit. Then charging process make compatible the pricing data to the usage of resource to an amount of money that we called charge. This charge has to paid by customer. And billing process obviously  informs customer about the billing information[7]. In fact accounting on Mobile network means the act keeping the records for all user’s usage of the source. The primary aim could be billing for any user but for security reasons we need to know each users logon and logout time, visited websites, amount of download and upload and so on.

 

4. New Mechanism

 4.1.  Mobility Message Authentication with a Cookie File

This section defines a new mechanism in mobility message authentication option that can be use to secure Binding Update and Binding Acknowledgement messages in mobile IPV6 networks. This mechanism is able to used along with IPsec or preferably as an new mechanism to authenticate Mobile node in communication with Home agent or foreign agent to Binding Update and Binding Acknowledgement messages whenever we don’t have IPsec infrastructure in our network. The simulation of the Mobile IPV6 protocols is based on the implementation of Mobile IPV6 in Network Simulator 2 (NS2). Overall implementation is based on home station, correspondent node and mobile agents. In fact base station agent will implement the functionality of home agent and foreign agent. This agent will create the Broadcasting area. This area will re-set every second. Mobile IPV6 agent finds the advertisement and registers with home agent and foreign agent based on protocol. The registration timeout for Mobile IPV6 protocol has set for one second. It means every second updating of registration will happen. For simulation we developed a simulated Mobile IPV6 network that considers to delay and payload.  Also for the simulation of the authentication with a C++ code  home agent will create a cookie file as a identity file. Based on our assumption the Mobile Node has registered with the home agent before leaving it’s subnet. The Mobile Node as a personal computer has some specific details that it can save them in a cookie as a file and then encrypt the file[10]. Home Agent MUST include this option in the BA if it received this option in the corresponding BU and Home Agent has a shared-key-based mobility security association with the Mobile Node[2]. 

 

4.2. New Care-of Address and Binding Update

After detection that a Mobile Node has moved the network, new CoA allowed to access to the network, but it must inform its Home Agent regarding the new location of Mobile Node. It’s a big concern in mobility that whenever a Mobile Node lost it’s connectivity with its last router, until it informs its Home Agent about its new location, all messages that sent to it will lost and also it will not able to send any packet to any of correspondent nodes. Actually a Mobile Node registers its new Care of Address to its HA via sending a binding update message. Then Home agent does acknowledge this update by replying a binding acknowledgement and from that time is able to tunnel the packets from Mobile Node’s home address (HoA) to the Mobile Node’s in new location. In the last step, The Mobile Node informs all of its Correspondent Node, its new location and that it is reachable with this new Care of Address. It means after registering, the Mobile Node sends a BU to all CN to inform them about its new location. By the way, there is an additional procedure for following that BUs are sent to all CNs. This one called Return Routability (RR) test.

  

4.3. WAP Infrastructure with CookiesWAP protocol is a service enabler that is located between internet and mobile networks in the service layer. The service layer includes of different service enablers for mobile nodes and mobile applications. The WAP protocol works like a secured tunnel from the mobile node to the  service layer. All IP packets from a mobile node will transport via three layers of mobile networks: connectivity layer, control layer, and service layer.  

4.4. Design and Implementation

Mobile IPv6 authentication relies fundamentally on IPv6 protocol functions as a standard protocol and IPv6 neighbour discovery as well[1]. It’s obvious that the latency can significantly affect during following components in IPV6 Mobility[13]:

• Movement detection time (td): The time to detection and establishment for Mobile Node, when it moves to a new location. For example the discovery of a new router.

• IPV6 Care-of-Address configuration time (ta):

The time between the establishment of movement and configuration of a globally routable IPv6 address. Duplicate address detection test is partial of this time[2].

• Context establishment time (tc): The time between establishment of a routable care-of address and the establishment of the suitable context state.

• Binding registration time (tr): The time between the sending of a binding update signal to the Home Agent to the receipt of an acknowledged Binding Update.

• Route optimization time (to): The time from registering of new Care of Address to completing route optimization with Correspondent Nodes. This time includes the return routability procedure time if exist, it must calculate before a Binding Update is sent by Mobile Node to a Correspondent Node[8].

In fact , the total Mobile IPV6 configuration delay (th) can be defined as the sum of these mentioned latency times as follows:

Formula 1: th = td + ta + tc + tr + to

  

4.4.1.  Movement Detection Time

The movement of detection time (td) is the sum of two separate latency time: First, Link of switching delay (Tl2) which is the time delay regarding to re-association of the wireless subnet’s Access Point and Second, Link-local IPv6 address configuration delay (Tll), which is the time between the first time that Mobile Node meets a new link by receiving neighbor advertisement over its all nodes. It means movement detection time can be defined as:

Formula 2 : td = Tl2 + Tll

  

4.4.2. Care of Address Configuration Time

As we mentioned about the CoA configuration time (ta), it’s a starting time from the moment of the receipt of a router advertisement till the Duplicate Address Detection and update of the routing table will complete. For stateless IPv6 address auto-configuration ta  is included of the following delays:

Formula 3: ta = TpreAd + TAddConf + TDAD + TRoutUpdt

Meanwhile TpreAd is defined as:

TrtAd – TrtSol (if the router advertisement is requested)

TrtAdInterval / 2 (if router advertisement is cyclic)

TAddConf is the real time that Mobile Node needs to configure the address, like to Create an unique and globally routable IPv6 address. The time in stateful address auto-configuration, like DHCPv6 for Care of address can be defined as:

Formula 4: TAddConf = TDHCPaddReq + TDHCPaddResp + TRoutUpdat

In fact TDHCPaddReq and TDHCPaddResp  will represent the transmission delay caused by stateful configuration of a care of address via a DHCP server in Mobile IPV6 network[9].

 

4.4.3. Care of Address Registration Time

Care of Address registration time or tr is defined as the transmission delay caused within registration of the Mobile Node Care of Address with its Home Agent.

Formula 5: tr = RTMN-HA + BUproc + BAproc

 

5. Create a Code to Perform MPV6 Authentication

On the File menu, point to New, then Project. Click Visual C++ Projects under Project Types, and then we click Mobile Web Application under Templates.

      “In the next step, we should add the following code to the Web.config file:”

  

     

        

           

        

     

  

  

               

 

  

To add a Mobile IPV6 authentication Web Form we should perform these steps:

First, click Add New Item on the Project Menu, then Click on Mobile Web Form and finally type Login.aspx in the Name box.

We can create the following controls from the Mobile IP Controls section

of the toolbox:Collapse this tableExpand this table

 

Control Type

Control Name

Control Text

Label

Label1

Type User Name

TextBox

txtUserName

Label

Label2

Type Password

TextBox

txtPassword

Command

cmdLogin

  Log in

Label

Error

Now we can click on Log in and open the code-behind page.

Then we should add the following code in the page:

private void cmdLogin_Clk(Obj sender, Event Args)

   {

      if(IsAuthenticated(txtUsername.Text, txtPassword.Text))

      {

MobileIPAuthentication.RedirectFromLogin(txtPassword.Text,true);

      }

      else

      {

         Error.Text = “Check the credentials”;

      }

   }

 

private IsAuthenticated(String user, String password)

{//Or call the cookie file which has been created for authentication/

   if(FormsAuthentication.Authenticate(user, password))

   {

      return true;

   }

   else

   {

      return false;

    }

}

We can add a Label control on the page, and change the text of the Label control to

“Mobile IPV6 Authenticated!”

 

6. Delay Calculation and analyze

6.1.  Authentication Delay Calculation

In this section, we quantitatively calculate and analyze the times of different phases of authentication on the security and system performance in Cookie ID based authentication and IPsec protocol with some assumption, which is the first step of the work for build up a relationship between the security and QoS[3]. Moreover the effect on the mobility security, authentication mechanism also affects on authentication delay, cost, number of message exchange, call dropping and etc[2]. Data encryption/decryption in each router involves some security processing latencies. We consider that an IPSec Mobile Network in each router take the same time. This latency lsec is evaluated with the following equation:

 Formula 7 :  lsec = Dpacket

                                     R

where Spacket is the data packet size (in bit) and R is the router encryption/decryption processing capability (in bit/s). In our assumption R is 1Mbit/Sec like a normal router. The authentication delay time is defined as the time from whenever  a Mobile Node sends out the authentication request till the time that Mobile Node receives the authentication reply. The problem is during this delay,  any data can be transmitted, which may interrupt or even disconnect the connections. Therefore, the call dropping will increased with the increase of authentication delay time[2]. In the other hand authentication cost is defined as the processing and signaling cost for cryptography. The total number of  messages from the Mobile Node, Foreign Node and Home agent could be large if the distance between them is long[14]. It should be considered, the mobility technique and traffic mechanisms will make the authentication frequently in different scenarios because the authentication will start whenever a Mobile Node establish a communication session.

 

Symbol

                                       Description

Ttr

Transmission time for Mobile Node

Tu

Update Binding Time

Ta

Acknowledgment  sending/receiving Time

Ted

Encryption/Decryption Time

Tr

Registration Time

Ts

Authentication request service and waiting time

Th

Home Agent updating time

Table 1

Formula 8 :

 Tsum = Ttr +  Tu + Ta +  Ted + Tr + Ts + Th

 6.2. Latency and Analyze Our Mechanism

Practical of Mobile IPV6 is likely to occur where a private network is deployed over the Internet. It means this situation can hint that Foreign Agent belongs to a another subnet wants to provide mobility services. For any accounting and billing purposes, the Foreign Agent needs to track of the usage of its services by mobile nodes. We simulate the Authentication protocol of Mobile IPV6 Transport Mode. Actually the major reason for simulation is representation with the least expensive computational authentication method.  A cookie based authentication is used between the Mobile Node and Home Agent. The second association will establish between Foreign Agent and Home Agent. With the expansion of mobile security protocols and the growth of internets, all networks are trying to securely extend their wireless networks over the public infra-structre, is called Virtual Private Networks or VPN. Cookie identity authentication’s  functionality consists of two phases: In the first phase, mobile node and home agent involved in communication establishment and in the second phase , the home agent and foreign agent will communicate for send/receive the cookie file which is belong to mobile ipv6 node. The major difference between this two phases is that phase 1 will happen in the same subnet and naturally it’s faster and easier to complete, but phase 2 must establish a communication between two different subnet. In phase 2 we recommend  to establish a tunnel for higher security. The attributes of cookie file which is include Mac address, User name, Password and may extra information defined by the encryption algorithm and authentication mechanism. Based on our assumption the maximum authentication message size would be 4096 bytes or 4KB, the transmission delay is considered 40 milliseconds, and we assume 4 Mbps for our mobile network capacity. Also IP Configuration latency on Local Site is around 20 msec and on different subnets this latency would be around 160-200 msec in Cisco standard. As a average it’s considered 180 msec.

Formula 9 : IPconf-latn-local= 20 Msec,

Formula 10 : IPconf-latn-global = 180 Msec

There is an additional factors should be considered. There are additional bytes added to each packet of data sent to control errors and routing information as well. The actual numbers of these codes depend on the packet size and also protocol used in Mobile network. Generally, a typical packet of data sent will be about 90% and 10% or a bit more belongs to overhead. In order to send 4096 Bytes of data about 4506 bytes would actually need to be transmitted.In a router with 16 MegaBITs/Sec speed transfer rate is equal to 2MB/Sec. Our Cookie file with 4506 byte would take time about 0.0023 seconds to send, assuming the source can continuously send the file and also the receiver can process it that fast and there no lost packets that need to be resent. In 802.11X protocol, router will advertise every second. It means in the best case a Mobile Node might wait about 0 Sec and in the worst case it might to wait 1 Sec for next advertising of router and join to it. We assume 0.5 Sec for all cases as a average waiting, whenever a Mobile Node wants to find and ask a router to join to the new subnet.

 Formula 11 :           File Size(Kbyte)

 Time Taken = ——————————— + Router delay (Sec)

                         Bandwidth Speed(KB/Sec)

 

                Action

In IPsec     (Sec)

In Cookie ID (Sec)

         Result

1st Exchange

      0

         0

 

For the first inquiry and Second

exchange both are the same

2nd Exchange

  (Formula 11)=

         4506b

2,000,000b/sec

 + 0.5=0.5023sec

                                                  

          

         0.5023

       

           0.5023

Initial to Update binding (Formula 10)+Router Delay

        

         0.6800

 

             —

 

Update Binding is a Must in IPsec

 

Respond to Updating (Formula 10)

       

         0.1800

     

             —

Refer to Home Agent(Router Delays,10)

0.5+0.5+0.18=1.1800

 

 

      

               –

      

         1.1800

 

In Our Mechanism MN refer to HA

Sending Cookie File from HA to CN  (Formula 11)=

         4506b

2,000,000b/sec

 + 0.5=0.5023sec

 

     

               —

       

             0.5023

 

HA will send the created ID cookie file to CN

 

Sending/Receiving Acknowledgment

Formula 11:

0.5+0.5=1 Sec

 

         1.0000

 

             –

 

In IPsec Acknowledgment transaction must updated

 

Encryption/Decryption By Tunneling

Formula7 :

 lsec = Dpacket =

                   R

       4065Byte     = 0.0325Sec

125,000Byte/Sec

 

     

             —

   

           0.0325

 

Cookie file must encrypt and

 decrypt for security reason

Care of Address

Formula 9:

IPconf-latn-local= 20 Msec,

 

        

          0.0200

 

          0.0200

 

Assign new IPV6 address to MN

Updating HA

(Formula 11)=

         4506b

2,000,000b/sec

 + 0.5=0.5023sec

 

        

          0.5023

 

          0.0023

 

HA already had ID from MIPV6,but in IPsec full

 info must updated

Total Time (Formula 8)            2.8846 Sec    2.2394 Sec

Table 2 : Timing calculation

 

Saving time: 2.8846 – 2.2394 = 0.6452 Sec         Efficiency on time saving : % 22

 

7. Conclusion

We have described secured authentication Mobile IPv6 mechanism and used in the standard protocol such as IPSec. In Mobile IP network techniques, some features are unconventional because of globally working of protocols and without any global infrastructure for security challenges. The quantitative analysis and design of Mobile IPV6 authentication with respect to the IPSec create more challenges about the authentication in IPV6 wireless networks. Overall time in IPSec in our assumption with 4KB file amd 2MB/Sec router bandwidth is  2.8846 Sec. But in our mechanism with Cookie ID it decreases to  2.2394Sec . It means saving time would be 0.6452 Sec and the efficiency would be “.

Note that we considered latency time for encryption/decryption via a tunnel from HA to CN, and obviously it takes time and cost for our mechanism[11]. We believe without making strong security, any protocol and mechanism on mobility infrastructure will not get a positive response. As result shows encryption/decryption time for Cookie ID file is  0.0325 Sec, that this time will be higher for bigger files. This time has not calculated and mentioned for IPsec protocol, because although it’s strongly recommended on IPSec, but its not a Must[5]. The only disadvantage of Cookie ID mechanism could be creating cookie files on the storage of authenticator server. We can ignore these small files, because as we mentioned the size of cookie file is 4KB. Also task schedule can be configure for disk cleanup monthly, weekly or daily. It can erase these un-useful files from the storage to prevent of any confusing and conflict.

  

   References:

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[2] C. Blondia, O. Casals, Ll. Cerdà, N. Van den Wijngaert, G. Willems, P.  De Cleyn,” Performance Comparison of Low Latency Mobile IP , INRIA Engineering Journal, Sophia Antipolis, pp., March 2008.

[3] Huachun Zhou?,†, Hongke Zhang and Yajuan Qin, An authentication method for proxy mobile IPv6 and performance analysis, Institute of Electronic Information Engineering, Beijing Jiaotong University, Sep 2008

[4] P. Calhoun, T. Johansson, C. Perkins, T. Hiller: Diameter Mobile IPv4 Application, IETF RFC 4004, August 2008.

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[6] M.S. Bargh, R.J. Hulsebosch, E.H. Eertink, A. Prasad: Fast Authentication Methods for Handovers between IEEE 802.11 Wireless LANs, ACM Press, Sep 2004.

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[8] T. Narten, E. Nordmark, W. Simpson, “Neighbor Discovery for IP Version 6 (IPv6)”, IETF RFC2461, August 2005.

 [9] K. Chowdhury, A. Yegin: MIP6-bootstrapping via DHCPv6 for the Integrated Scenario, IETF draft, June 2006.

[10] J. Chen and K.J.R. Liu. Joint Source-channel Multi-stream Coding And Optical Network Adapter Design For Video Over IP . IEEE Transactions on Multimedia, 4(1):3–22, March 2002.

[11] Da Wei, Yanheng Liu, Xuegang Yu, Xiaodong Li: Research of Mobile IPv6 Application Based On Diameter Protocol, IEEE Computer Society, 2006.

[12] P. Funk, S. Blake-Wilson: EAP Tunneled TLS Authentication Protocol Version 1, IETF draft, March 2006.

[13] A. Diab, A. Mitschele-Thiel,“ Minimizing Mobile IP Handoff Latency,” 2nd International Working Conference on Performance modeling and Evaluation of Heterogeneous Networks (HET-NET Journal, U.K., July 2006.

[14] C.F. Grecas, S.I. Maniatis, and I.S. Venieris. Towards the Introduction of the Asymmetric Cryptography. In Proceedings. Sixth IEEE Symposium on Computers and Communications, 2001, July 2001.

[15] J. C. Chen, Y. P. Wang: Extensible Authentication Protocol (EAP) and IEEE 802.1X: Tutorial and Empirical Experience, IEEE Radio Communications, Dec 2005.

 

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As a selective serotonin re-uptake inhibitor or SSRI drug, the mechanism of action of fluoxetine is by increasing the level of serotonin in the brain. It has been suggested that patients with depression have lower levels of serotonin in their brain. Fluoxetine eases the symptoms of depression by treating this serotonin imbalance in the brain.

 

Serotonin is one of the neurotransmitters present in the brain which is easily reabsorbed once it is released. The mechanism of action of fluoxetine is to inhibit or slow down the metabolism of this neurotransmitter in order for the brain to have higher levels of serotonin. Patients with increased levels of serotonin were found to usually recover from their symptoms.

 

SSRI drugs like fluoxetine have been found to also help in the growth of new neurons, commonly called nerve cells, in patients. Neurons are very essential in facilitating information in the brain. It has been suggested that growth of new neurons allows the brain to have more room for processing new thoughts, memory, emotions, and motivations. Fluoxetine and other serotonin inhibitors hastens the growth of new nerve cells in the part of the brain responsible for improving the moods of the patients.

 

Since it often takes a longer time to treat the symptoms of depression, increasing fluoxetine doses is usually done. Doctors usually start a patient’s medication on a lower dose before gradually increasing fluoxetine doses as the symptoms react on the drug. Improvement and prevention of a possible relapse of depression are the usual effects of increasing fluoxetine doses in patients.

 

Patients should not be alarmed that toxic effects from increasing fluoxetine levels may arise once their doctor suggests a higher dose. SSRI drugs are considered one of the safest antidepressant drugs that also cause the least number of side effects. Although SSRI drugs treat depression in the same manner, their side effects may vary in different patients. Possible side effects like nausea, diarrhea, headache, lack of sexual drive, drowsiness, and insomnia may be experienced but this depends in every patient. Some patients may have these side effects while others may not. These side effects can also diminish as the doctor adjusts the fluoxetine dose prescribed.

 

Increasing the level of fluoxetine dose to be taken is just normal in long-term medications and it doesn’t mean that doctors will always increase the patients’ dose. It is only done as the symptoms progress. This increases the patients chance of recovery and reduces the risk that the symptoms may come back once the medication is complete. Once the symptoms of depression diminish, doctors can start to decrease the fluoxetine dose to be taken. In this way, withdrawal symptoms from suddenly stopping the medication can be prevented. The dose may be decreased gradually every 2 weeks until the patient no longer has to take any dose.

 

Fluoxetine is one of the dependable drugs for the treatment of depression. It is important that patients understand that increasing fluoxetine doses is not intended to cause them any harm and that it is just a normal part of their treatment. It is one way of improving the drug’s efficacy in treating depression.

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Finally someone has come up with a cure for unattractive television sets that can destroy the balance and pleasing ambience of a room. They didn’t do it by reinventing televisions to look better, but instead savvy engineers designed special TV lift mechanisms. These devices can be used with practically any television set and they work by raising or lowering the viewing screen. When you want to watch TV the lift raises it up like a small elevator, and when the television is turned off it goes back down into its concealed storage area or customized hiding compartment.

 

Ideally, consumers should choose a TV lift mechanism that is not only sturdy, strong, stable, and not bulky, but one that also has no ugly and visible struts, gears, or mechanical devices. After all, the goal of installing a quality TV lift mechanism is to remove all of the visual and spatial clutter. Inferior lift designs might hide everything out of sight when the television is not being watched, but they create an eyesore when the unit is operating, and that can defeat the whole purpose of having a lift mechanism installed. 

 

Another critical aspect of choosing a sophisticated lift is in terms of how quietly it functions. Some poorly made versions can be so loud that the process of moving the television up or down grates on the nerves and the eardrums. So do a test drive or inquire from the manufacturer ahead of time to ensure that the mechanism works well but also works quietly. The best TV lifts are supposed to be “not seen and not heard,” and by shopping around for a reliable brand with a dependable warranty and a design that works smoothly and quietly it is possible to invest in a unit that will deliver years of satisfaction and convenience.

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 CDM is a huge business opportunity for CA profession in 2009 and in future. 

In India there is huge initiative by govt. of India to avail carbon credits.

CA professional can gain good business and consulting opportunity by following ways:

Clean Development Mechanism (CDM) allows industrialized/developed countries to invest in emission reduction projects in developing countries that assist the developing countries in achieving sustainable development, and that generate Certified Emission Reductions (CER) for use by the investing countries or companies against their own emissions limitation targets. 

As per the Kyoto Protocol, some of the sectors, investments in which may qualify for CDM credits, are:

The following chart depicts the entire process of CDM cycle till the issuance and transaction of CERs.

I    Project Implementation

  

a.   Project identification.

b.   Project Construction

c.   Project Operation

II   Kyoto Approvals

III   CER Transaction

3.      CA can help to adopt the green business by creating sustainable business practice:  By measuring bottom line returns by reducing wastage and lowering the cost of energy consumption. The secret behind any successful company depends on both creating shareholder value and operating responsibly.  Today, the competitive advantage of any business organization is directly linked to its efficiency in terms of consumption of limited resources, less pollution and higher quality products.  Going forward, the purpose of any business should be to adopt sustainable practices more than generating short-term shareholder value. These practices include building trust among the public and maintaining a healthy environment in which to do business.

A C.A. can advised business in following green areas which will lead to:

4.  Carbon credit trading is the new buzz word which allows trading in CER units generated over deferent stock exchanges in world like:

  

For more articles on clean development mechanism(CDM) visit -  http://www.onlinecarbonfinance.com/

onlinecarbonfinance.com is powered by Ecodrive2. Ecodrive2 is a trust dedicated to environmental awareness with prime focus on carbon credit. Ecodrive2 is a team of professionals, researcher, Industrialist and citizens working to reduce global footprint.

An international conference in 11 December 2009 will be held in Delhi, India to discuss issues on cleaner technology , wind power, solar power, carbon credit markets, buyers & sellers & Kyoto protocol. The International conference will focus on carbon mitigation & carbon neutrality. Carbon credit platform will help to reduce global warming by measuring carbon footprint through CDM tools. International conference will attract global carbon experts.

International Carbon Credit Conference 2009

Venue: New Delhi

Date: 11 & 12 December 2009

Time: 9:00 a.m. to 5:00 p.m.

The program will include interactive and extensive session on various issues pertaining to the carbon trade. It will give a networking opportunity with leading carbon project developers and carbon validators of the Indian carbon markets with expert global companies or consultants. The International Carbon Credit conference 2009 will also provide the expertise and knowledge to successfully enter the carbon market. The International conference will bring cabon credits buying house in direct interaction with Indian carbon market.

Each session of International Carbon Credit conference 2009 will be led by an expert, followed by Question & Answer session that will lead to comprehensive interaction.

 

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A movement is a term used in watch-making. It is the method that measures the passage of time and shows the current time. The movement can be mechanical, electronic or both. Mechanical Movements: In this the escapement mechanism is used to control the watch by converting the unwinding process into a period release of energy. The gear system is controlled by a balance wheel and a balance spring or a hairspring. To reduce the effect of gravitation an additional part called the tourbillon is used. As the tourbillon has a complex design and because it is expensive, they are implemented in high-end watches only. Tuning fork mechanism is used in electromechanical-movement watches but soon became a thing of the past after the advent of electronic quartz watches. The mechanical movement is less accurate than the electronic movements – shows errors in seconds – and is sensitive to temperature and position. However, the mechanical movement watches are still attractive as it has the old-world charm to it. Electronic Movements: In this mechanism there are few or no moving parts at all. A small quartz crystal and the principle of piezoelectric effect is used to stabilize the time. The crystal has a quartz oscillator which can be activated by a suitable frequency and can be used to maintain the time accurately. The archetype of quartz watch was tested in Switzerland in 1962 and Seiko 35 SQ Astron became the first watch which used this mechanism; it was released in 1969. Some watch makers also combine this mechanism with mechanical movements, like the Seiko Spring Drive which was release in 2005. Modern watches synchronise itself by receiving signals from atomic clocks, radio signals, GPS satellite signals, DCF77 signal (Europe), and WWVB signal (US). These type of watches not only synchronize the time but also the date, check if the year is a leap-year, and show the present condition of daylight saving time (if it is ON or OFF).

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When you decide to add a Murphy bed into your home, determining exactly what you want and where to find it can seem a daunting task. It is important to consider each aspect of a Murphy bed individually, to ensure that the product you purchase is exactly what you are looking for. One of the first factors to take into consideration when determining what type of Murphy bed is right for you is the mechanism used. The mechanism in a Murphy bed is the most basic element of its construction, as the mechanism dictates nearly all of the facets of the bed’s structure. There are several different types of mechanisms, as well as a number of manufacturers producing beds for each type. The two main varieties of Murphy bed mechanisms are spring mechanisms and piston mechanisms. Each style has unique qualities, and can be essential in your decision making process.

Spring mechanisms are part of the traditional Murphy bed system. They usually consist of a heavy duty compressed steel spring system that may or may not be concealed within the frame of the Murphy bed.

Integration into Cabinetry

When concealed within the framework of the Murphy bed, the spring mechanism may require specialized cabinetry, such as bi-fold doors or cabinets, which can hinder the use of other storage pieces adjacent to the Murphy bed.

Adjusting/Sagging

Spring mechanisms are counter balanced, and enhance the ease of lowering and lifting your Murphy bed. These springs may require adjustment after several years of use, as the springs can fatigue and stretch over time. This fatigue may lead to the Murphy bed sagging out of the frame if not adjusted. The ability to adjust the mechanism does, however, give you the opportunity to dictate the level of tension in the springs, which is impossible in systems utilizing piston mechanisms.

The second main type of mechanism used in Murphy bed systems is the piston mechanism. These pistons generally utilize either gas or air pressure in their function, and provide generous support when raising and lowering the Murphy bed.

Locks

A benefit to choosing a Murphy bed that operates with a piston mechanism is the use of a locking device. These locks keep the Murphy bed securely inside of the cabinet when not in use and are a valuable safety feature. Murphy bed systems that utilize piston mechanism experience a much lower possibility of fatigue and sagging, which significantly extends the longevity of the product.

Zero-Adjustment

These mechanisms require no adjustment, and are concealed within the frame of the Murphy bed. Because pistons cannot be adjusted, however, proper installation is crucial to promote the longevity of the mechanism, as piston mechanisms cannot be adjusted once installed. Determining which type of Murphy bed mechanism is right for you and your home can seem a difficult task. It is important to take your time when deciding, and to explore all of the possible options before making your final decisions.

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This definition implies that a device can only be called a “robot” if it contains a movable mechanism, influenced by sensing, planning, and actuation and control components. It does not imply that a minimum number of these components must be implemented in software, or be changeable by the “consumer” who uses the device; for example, the motion behavior can have been hard-wired into the device by the manufacturer.

 

So, the presented definition, as well as the rest of the material in this part of the Book, covers not just “pure” robotics or only “intelligent” robots, but rather the somewhat broader domain of robotics and automation. This includes “dumb” robots such as: metal and woodworking machines, “intelligent” washing machines, dish washers and pool cleaning robots, etc. These examples all have sensing, planning and control, but often not in individually separated components. For example, the sensing and planning behavior of the pool cleaning robot have been integrated into the mechanical design of the device, by the intelligence of the human developer.

 

Robotics is, to a very large extent, all about system integration, achieving a task by an actuated mechanical device, via an “intelligent” integration of components, many of which it shares with other domains, such as systems and control, computer science, character animation, machine design, computer vision, artificial intelligence, cognitive science, biomechanics, etc. In addition, the boundaries of robotics cannot be clearly defined, since also its “core” ideas, concepts and algorithms are being applied in an ever increasing number of “external” applications, and, vice versa, core technology from other domains (vision, biology, cognitive science or biomechanics, for example) are becoming crucial components in more and more modern robotic systems.

 

This part of the WEBook makes an effort to define what exactly is that above-mentioned core material of the robotics domain, and to describe it in a consistent and motivated structure. Nevertheless, this chosen structure is only one of the many possible “views” that one can want to have on the robotics domain.

 

In the same vein, the above-mentioned “definition” of robotics is not meant to be definitive or final, and it is only used as a rough framework to structure the various chapters 

 

Components of robotic systems

 

 

 

 

 

 

 

 

This figure depicts the components that are part of all robotic systems. The purpose of this Section is to describe the semantics of the terminology used to classify the chapters in the WEBook: “sensing”, “planning”, “modeling”, “control”, etc.

 

The real robot is some mechanical device (“mechanism”) that moves around in the environment, and, in doing so, physically interacts with this environment. This interaction involves the exchange of physical energy, in some form or another. Both the robot mechanism and the environment can be the “cause” of the physical interaction through “Actuation”, or experience the “effect” of the interaction, which can be measured through “Sensing”.

 

Robotics as an integrated system of control interacting with the physical world.

 

Sensing and actuation are the physical ports through which the “Controller” of the robot determines the interaction of its mechanical body with the physical world. As mentioned already before, the controller can, in one extreme, consist of software only, but in the other extreme everything can also be implemented in hardware.

 

Within the Controller component, several sub-activities are often identified:

 

Modelling. The input-output relationships of all control components can (but need not) be derived from information that is stored in a model. This model can have many forms: analytical formulas, empirical look-up tables, fuzzy rules, neural networks, etc.

 

The name “model” often gives rise to heated discussions among different research “schools”, and the WEBook is not interested in taking a stance in this debate: within the WEBook, “model” is to be understood with its minimal semantics: “any information that is used to determine or influence the input-output relationships of components in the Controller.”

 

The other components discussed below can all have models inside. A “System model” can be used to tie multiple components together, but it is clear that not all robots use a System model. The “Sensing model” and “Actuation model” contain the information with which to transform raw physical data into task-dependent information for the controller, and vice versa.

 

Planning. This is the activity that predicts the outcome of potential actions, and selects the “best” one. Almost by definition, planning can only be done on the basis of some sort of model.

 

Regulation. This component processes the outputs of the sensing and planning components, to generate an actuation setpoint. Again, this regulation activity could or could not rely on some sort of (system) model.

 

The term “control” is often used instead of “regulation”, but it is impossible to clearly identify the domains that use one term or the other. The meaning used in the WEBook will be clear from the context.

 

Scales in robotic systems

 

The above-mentioned “components” description of a robotic system is to be complemented by a “scale” description, i.e., the following system scales have a large influence on the specific content of the planning, sensing, modelling and control components at one particular scale, and hence also on the corresponding sections of the WEBook.

 

Mechanical scale. The physical volume of the robot determines to a large extent the limites of what can be done with it. Roughly speaking, a large-scale robot (such as an autonomous container crane or a space shuttle) has different capabilities and control problems than a macro robot (such as an industrial robot arm), a desktop robot (such as those “sumo” robots popular with hobbyists), or milli micro or nano robots.

Spatial scale. There are large differences between robots that act in 1D, 2D, 3D, or 6D (three positions and three orientations).

 

Time scale. There are large differences between robots that must react within hours, seconds, milliseconds, or microseconds.

 

Power density scale. A robot must be actuated in order to move, but actuators need space as well as energy, so the ratio between both determines some capabilities of the robot.

 

System complexity scale. The complexity of a robot system increases with the number of interactions between independent sub-systems, and the control components must adapt to this complexity.

 

Computational complexity scale. Robot controllers are inevitably running on real-world computing hardware, so they are constrained by the available number of computations, the available communication bandwidth, and the available memory storage.

 

Obviously, these scale parameters never apply completely independently to the same system. For example, a system that must react at microseconds time scale can not be of macro mechanical scale or involve a high number of communication interactions with subsystems.

 

Background sensitivity

 

Finally, no description of even scientific material is ever fully objective or context-free, in the sense that it is very difficult for contributors to the WEBook to “forget” their background when writing their contribution. In this respect, robotics has, roughly speaking, two faces: (i) the mathematical and engineering face, which is quite “standardized” in the sense that a large consensus exists about the tools and theories to use (“systems theory”), and (ii) the AI face, which is rather poorly standardized, not because of a lack of interest or research efforts, but because of the inherent complexity of “intelligent behaviour.” The terminology and systems-thinking of both backgrounds are significantly different, hence the WEBook will accomodate sections on the same material but written from various perspectives. This is not a “bug”, but a “feature”: having the different views in the context of the same WEBook can only lead to a better mutual understanding and respect.

 

Research in engineering robotics follows the bottom-up approach: existing and working systems are extended and made more versatile. Research in artificial intelligence robotics is top-down: assuming that a set of low-level primitives is available, how could one apply them in order to increase the “intelligence” of a system. The border between both approaches shifts continuously, as more and more “intelligence” is cast into algorithmic, system-theoretic form. For example, the response of a robot to sensor input was considered “intelligent behaviour” in the late seventies and even early eighties. Hence, it belonged to A.I. Later it was shown that many sensor-based tasks such as surface following or visual tracking could be formulated as control problems with algorithmic solutions. From then on, they did not belong to A.I. any more.

 

 

 

Robotics Technology

 

Most industrial robots have at least the following five parts:

 

Sensors, Effectors, Actuators, Controllers, and common effectors known as Arms.

 

Many other robots also have Artificial Intelligence and effectors that help it achieve Mobility.

 

This section discusses the basic technologies of a robot. Click one of the links above or use the navigation bar menu on the far right.

 

Robotics Technology – Sensors

 

Most robots of today are nearly deaf and blind.  Sensors can provide some limited feedback to the robot so it can do its job.  Compared to the senses and abilities of even the simplest living things, robots have a very long way to go.

 

The sensor sends information, in the form of electronic signals back to the cfontroller.  Sensors also give the robot controller information about its surroundings and lets it know the exact position of the arm, or the state of the world around it.

Sight, sound, touch, taste, and smell are the kinds of information we get from our world.  Robots can be designed and programmed to get specific information that is beyond what our 5 senses can tell us. For instance, a robot sensor might “see” in the dark, detect tiny amounts of invisible radiation or measure movement that is too small or fast for the human eye to see.

 

Here are some things sensors are used for:

 

Physical Property

 Technology

 

Contact Bump, Switch

Distance Ultrasound, Radar, Infra Red

Light Level Photo Cells, Cameras

Sound Level microphones

Strain Strain Gauges

Rotation Encoders

Magnetism Compasses

Smell Chemical

Temperature Thermal, Infra Red

Inclination Inclinometers, Gyroscope

Pressure Pressure Gauges

Altitude Altimeters

 

    Sensors can be made simple and complex, depending on how much information needs to be stored.  A switch is a simple on/off sensor used for turning the robot on and off.  A human retina is a complex sensor that uses more than a hundred million photosensitive elements (rods and cones).  Sensors provide information to the robots brain, which can be treated in various ways.  For example, we can simply react to the sensor output: if the switch is open, if the switch is closed, go. 

 

Levels of Processing

 

    To figure out if the switch is open or closed, you will need to measure the voltage going through the circuit, that’s electronics.  Now lets say that you have a microphone and you want to recognize a voice and separate it from noise; that’s signal processing.  Now you have a camera, and you want to take the pre-processed image and now you need to figure out what those objects are, perhaps by comparing them to a large library of drawings; that’s computation.  Sensory data processing is a very complex thing to try and do but the robot needs this in order to have a “brain”.  The brain has to have analog or digital processing capabilities, wires to connect everything, support electronics to go with the computer, and batteries to provide power for the whole thing, in order to process the sensory data.  Perception requires the robot to have sensors (power and electronics), computation (more power and electronics, and connectors (to connect it all). 

 

Switch Sensors

 

 Switches are the simplest sensors of all.  They work without processing, at the electronics (circuit) level.  Their general underlying principle is that of an open vs. closed circuit.  If a switch is open, no current can flow; if it is closed, current can flow and be detected.  This simple principle can (and is) used in a wide variety of ways.

 

Switch sensors can be used in a variety of ways:

 

contact sensors: detect when the sensor has contacted another object (e.g., triggers when a robot hits a wall or grabs an object; these can even be whiskers)

 

limit sensors: detect when a mechanism has moved to the end of its range

 

shaft encoder sensors: detects how many times a shaft turns by having a switch click (open/close) every time the shaft turns (e.g., triggers for each turn, allowing for counting rotations)

 

   There are many common switches: button switches, mouse switches, key board keys, phone keys, and others.  Depending on how a switch is wired, it can be normally open or normally closed.  This would of course depend on your robot’s electronics, mechanics, and its task.  The simplest yet extremely useful sensor for a robot is a “bump switch” that tells it when it’s bumped into something, so it can back up and turn away. Even for such a simple idea, there are many different ways of implementation.

 

Light Sensors

 

Switches measure physical contact and light sensors measure the amount of light impacting a photocell, which is basically a resistive sensor.  The resistance of a photocell is low when it is brightly illuminated, i.e., when it is very light; it is high when it is dark.  In that sense, a light sensor is really a “dark” sensor.  In setting up a photocell sensor, you will end up using the equations we learned above, because you will need to deal with the relationship of the photocell resistance photo, and the resistance and voltage in your electronics sensor circuit.  Of course since you will be building the electronics and writing the program to measure and use the output of the light sensor, you can always manipulate it to make it simpler and more intuitive.  What surrounds a light sensor affects its properties.  The sensor can be  shielded and positioned in various ways.  Multiple sensors can be arranged in useful configurations and isolate them from each other with shields.

 

Just like switches, light sensors can be used in many different ways:

 

Light sensors can measure:

 

light intensity (how light/dark it is)

 

differential intensity (difference between photocells)

 

break-beam (change/drop in intensity)

 

Light sensors can be shielded and focused in different ways

 

Their position and directionality on a robot can make a great deal of difference and impact

 

Polarized light

 

“Normal” light emanating from a source is non-polarized, which means it travels at all orientations with respect to the horizon.  However, if there is a polarizing filter in front of a light source, only the light waves of a given orientation of the filter will pass through.  This is useful because now we can manipulate this remaining light with other filters; if we put it through another filter with the same characteristic plane, almost all of it will get through.  But, if we use a perpendicular filter (one with a 90-degree relative characteristic angle), we will block all of the light.  Polarized light can be used to make specialized sensors out of simple photocells; if you put a filter in front of a light source and the same or a different filter in front of a photocell, you can cleverly manipulate what and how much light you detect. 

 

Resistive Position Sensors

 

    We said earlier that a photocell is a resistive device.  We can also sense resistance in response to other physical properties, such as bending.  The resistance of the device increases with the amount it is bent.  These bend sensors were originally developed for video game control (for example, Nintendo Powerglove), and are generally quite useful.  Notice that repeated bending will wear out the sensor.  Not surprisingly, a bend sensor is much less robust than light sensors, although they use the same underlying resistive principle.

 

Potentiometers

 

    These devices are very common for manual tuning; you have probably seen them in some controls (such as volume and tone on stereos).  Typically called pots, they allow the user to manually adjust the resistance.  The general idea is that the device consists of a movable tap along two fixed ends.  As the tap is moved, the resistance changes.  As you can imagine, the resistance between the two ends is fixed, but the resistance between the movable part and either end varies as the part is moved.  In robotics, pots are commonly used to sense and tune position for sliding and rotating mechanisms.

 

Biological Analogs

 

All of the sensors we described exist in biological systems

 

Touch/contact sensors with much more precision and complexity in all species

 

Bend/resistance receptors in muscles 

 

Reflective Optosensors

 

    We mentioned that if we use a light bulb in combination with a photocell, we can make a break-beam sensor. This idea is the underlying principle in reflective optosensors: the sensor consists of an emitter and a detector. Depending of the arrangement of those two relative to each other, we can get two types of sensors:

 

reflectance sensors (the emitter and the detector are next to each other, separated by a barrier; objects are detected when the light is reflected off them and back into the detector)

 

break-beam sensors (the emitter and the detector face each other; objects are detected if they interrupt the beam of light between the emitter and the detector)

 

    The emitter is usually made out of a light-emitting diode (an LED), and the detector is usually a photodiode/phototransistor.

 

    Note that these are not the same technology as resistive photocells. Resistive photocells are nice and simple, but their resistive properties make them slow; photodiodes and photo-transistors are much faster and therefore the preferred type of technology.

 

What can you do with this simple idea of light reflectivity? Quite a lot of useful things:

 

object presence detection

 

object distance detection

 

surface feature detection (finding/following markers/tape)

 

wall/boundary tracking

 

rotational shaft encoding (using encoder wheels with ridges or black & white color)

 

bar code decoding

 

    Note, however, that light reflectivity depends on the color (and other properties) of a surface. A light surface will reflect light better than a dark one, and a black surface may not reflect it at all, thus appearing invisible to a light sensor. Therefore, it may be harder (less reliable) to detect darker objects this way than lighter ones. In the case of object distance, lighter objects that are farther away will seem closer than darker objects that are not as far away. This gives you an idea of how the physical world is partially-observable. Even though we have useful sensors, we do not have complete and completely accurate information.

 

    Another source of noise in light sensors is ambient light. The best thing to do is subtract the ambient light level out of the sensor reading, in order to detect the actual change in the reflected light, not the ambient light. How is that done? By taking two (or more, for higher accuracy) readings of the detector, one with the emitter on, and one with it off, and subtracting the two values from each other. The result is the ambient light level, which can then be subtracted from future readings. This process is called sensor calibration. Of course, remember that ambient light levels can change, so the sensors may need to be calibrated repeatedly.

 

Break-beam Sensors

 

    We already talked about the idea of break-beam sensors. In general, any pair of compatible emitter-detector devices can be used to produce such a sensors:

 

an incandescent flashlight bulb and a photocell

 

red LEDs and visible-light-sensitive photo-transistors

 

or infra-red IR emitters and detectors

 

Shaft Encoding

 

Shaft encoders measure the angular rotation of an axle providing position and/or velocity info. For example, a speedometer measures how fast the wheels of a vehicle are turning, while an odometer measures the number of rotations of the wheels.

 

In order to detect a complete or partial rotation, we have to somehow mark the turning element. This is usually done by attaching a round disk to the shaft, and cutting notches into it. A light emitter and detector are placed on each side of the disk, so that as the notch passes between them, the light passes, and is detected; where there is no notch in the disk, no light passes.

 

If there is only one notch in the disk, then a rotation is detected as it happens. This is not a very good idea, since it allows only a low level of resolution for measuring speed: the smallest unit that can be measured is a full rotation. Besides, some rotations might be missed due to noise.

 

Usually, many notches are cut into the disk, and the light hits impacting the detector are counted. (You can see that it is important to have a fast sensor here, if the shaft turns very quickly.)

 

An alternative to cutting notches in the disk is to paint the disk with black (absorbing, non-reflecting) and white (highly reflecting) wedges, and measure the reflectance. In this case, the emitter and the detector are on the same side of the disk.

 

In either case, the output of the sensor is going to be a wave function of the light intensity. This can then be processes to produce the speed, by counting the peaks of the waves.

 

Note that shaft encoding measures both position and rotational velocity, by subtracting the difference in the position readings after each time interval. Velocity, on the other hand, tells us how fast a robot is moving, or if it is moving at all. There are multiple ways to use this measure:

 

measure the speed of a driven (active) wheel

 

use a passive wheel that is dragged by the robot (measure forward progress)

 

We can combine the position and velocity information to do more sophisticated things:

 

move in a straight line

 

rotate by an exact amount

 

Note, however, that doing such things is quite difficult, because wheels tend to slip (effector noise and error) and slide and there is usually some slop and backlash in the gearing mechanism. Shaft encoders can provide feedback to correct the errors, but having some error is unavoidable.

 

Quadrature Shaft Encoding

 

So far, we’ve talked about detecting position and velocity, but did not talk about direction of rotation. Suppose the wheel suddenly changes the direction of rotation; it would be useful for the robot to detect that.

 

An example of a common system that needs to measure position, velocity, and direction is a computer mouse. Without a measure of direction, a mouse is pretty useless. How is direction of rotation measured?

 

Quadrature shaft encoding is an elaboration of the basic break-beam idea; instead of using only one sensor, two are needed. The encoders are aligned so that their two data streams coming from the detector and one quarter cycle (90-degrees) out of phase, thus the name “quadrature”. By comparing the output of the two encoders at each time step with the output of the previous time step, we can tell if there is a direction change. When the two are sampled at each time step, only one of them will change its state (i.e., go from on to off) at a time, because they are out of phase. Which one does it determines which direction the shaft is rotating. Whenever a shaft is moving in one direction, a counter is incremented, and when it turns in the opposite direction, the counter is decremented, thus keeping track of the overall position.

 

Other uses of quadrature shaft encoding are in robot arms with complex joints (such as rotary/ball joints; think of your knee or shoulder), Cartesian robots (and large printers) where an arm/rack moves back and forth along an axis/gear.

 

Modulation and Demodulation of Light

 

We mentioned that ambient light is a problem because it interferes with the emitted light from a light sensor. One way to get around this problem is to emit modulated light, i.e., to rapidly turn the emitter on and off. Such a signal is much easier and more reliably detected by a demodulator, which is tuned to the particular frequency of the modulated light. Not surprisingly, a detector needs to sense several on-flashes in a row in order to detect a signal, i.e., to detect its frequency. This is a small point, but it is important in writing demodulator code.

 

The idea of modulated IR light is commonly used; for example in household remote controls.

 

Modulated light sensors are generally more reliable than basic light sensors. They can be used for the same purposes: detecting the presence of an object measuring the distance to a nearby object (clever electronics required, see your course notes)

 

Infra Red (IR) Sensors

 

Infra red sensors are a type of light sensors, which function in the infra red part of the frequency spectrum.  IR sensors consist are active sensors: they consist of an emitter and a receiver.  IR sensors are used in the same ways that visible light sensors are that we have discussed so far: as break-beams and as reflectance sensors.  IR is preferable to visible light in robotics (and other) applications because it suffers a bit less from ambient interference, because it can be easily modulated, and simply because it is not visible.

 

IR Communication

 

Modulated infra red can be used as a serial line for transmitting messages. This is is fact how IR modems work. Two basic methods exist:

 

bit frames (sampled in the middle of each bit; assumes all bits take the same amount of time to transmit)

 

bit intervals (more common in commercial use; sampled at the falling edge, duration of interval between sampling determines whether it’s a 0 or 1)

 

Ultrasonic Distance Sensing

 

As we mentioned before, ultrasound sensing is based on the time-of-flight principle. The emitter produces a sonar “chirp” of sound, which travels away from the source, and, if it encounters barriers, reflects from them and returns to the receiver (microphone). The amount of time it takes for the sound beam to come back is tracked (by starting a timer when the “chirp” is produced, and stopping it when the reflected sound returns), and is used to compute the distance the sound traveled. This is possible (and quite easy) because we know how fast sound travels; this is a constant, which varies slightly based on ambient temperature.

 

At room temperature, sound travels at 1.12 feet per millisecond. Another way to put it that sound travels at 0.89 milliseconds per foot. This is a useful constant to remember.

 

The process of finding one’s location based on sonar is called echolocation. The inspiration for ultrasound sensing comes from nature; bats use ultrasound instead of vision (this makes sense; they live in very dark caves where vision would be largely useless). Bat sonars are extremely sophisticated compared to artificial sonars; they involve numerous different frequencies, used for finding even the tiniest fast-flying prey, and for avoiding hundreds of other bats, and communicating for finding mates.

                                                         

Specular Reflection

 

A major disadvantage of ultrasound sensing is its susceptibility to specular reflection (specular reflection means reflection from the outer surface of the object). While the sonar sensing principle is based on the sound wave reflecting from surfaces and returning to the receiver, it is important to remember that the sound wave will not necessarily bounce off the surface and “come right back.” In fact, the direction of reflection depends on the incident angle of the sound beam and the surface. The smaller the angle, the higher the probability that the sound will merely “graze” the surface and bounce off, thus not returning to the emitter, in turn generating a false long/far-away reading. This is often called specular reflection, because smooth surfaces, with specular properties, tend to aggravate this reflection problem. Coarse surfaces produce more irregular reflections, some of which are more likely to return to the emitter. (For example, in our robotics lab on campus, we use sonar sensors, and we have lined one part of the test area with cardboard, because it has much better sonar reflectance properties than the very smooth wall behind it.)

 

In summary, long sonar readings can be very inaccurate, as they may result from false rather than accurate reflections. This must be taken into account when programming robots, or a robot may produce very undesirable and unsafe behavior. For example, a robot approaching a wall at a steep angle may not see the wall at all, and collide with it!

 

Nonetheless, sonar sensors have been successfully used for very sophisticated robotics applications, including terrain and indoor mapping, and remain a very popular sensor choice in mobile robotics.

 

The first commercial ultrasonic sensor was produced by Polaroid, and used to automatically measure the distance to the nearest object (presumably which is being photographed). These simple Polaroid sensors still remain the most popular off-the-shelf sonars (they come with a processor board that deals with the analog electronics). Their standard properties include:

 

32-foot range

 

30-degree beam width

 

sensitivity to specular reflection

 

shortest distance return

 

Polaroid sensors can be combined into phased arrays to create more sophisticated and more accurate sensors.

 

One can find ultrasound used in a variety of other applications; the best known one is ranging in submarines. The sonars there have much more focused and have longer-range beams. Simpler and more mundane applications involve automated “tape-measures”, height measures, burglar alarms, etc.

 

Machine Vision

 

So far, we have talked about relatively simple sensors. They were simple in terms of processing of the information they returned. Now we turn to machine vision, i.e., to cameras as sensors.

 

Cameras, of course, model biological eyes. Needless to say, all biological eyes are more complex than any camera we know today, but, as you will see, the cameras and machine vision systems that process their perceptual information, are not simple at all! In fact, machine vision is such a challenging topic that it has historically been a separate branch of Artificial Intelligence.

 

The general principle of a camera is that of light, scattered from objects in the environment (those are called the scene), goes through an opening (”iris”, in the simplest case a pin hole, in the more sophisticated case a lens), and impinging on what is called the image plane. In biological systems, the image plane is the retina, which is attached to numerous rods and cones (photosensitive elements) which, in turn, are attached to nerves which perform so-called “early vision”, and then pass information on throughout the brain to do “higher-level” vision processing. As we mentioned before, a very large percentage of the human (and other animal) brain is dedicated to visual processing, so this is a highly complex endeavor.

 

In cameras, instead of having photosensitive rhodopsin and rods and cones, we use silver halides on photographic film, or silicon circuits in charge-coupled devices (CCD) cameras. In all cases, some information about the incoming light (e.g., intensity, color) is detected by these photosensitive elements on the image plane.

 

In machine vision, the computer must make sense out of the information it gets on the image plane. If the camera is very simple, and uses a tiny pin hole, then some computation is required to compute the projection of the objects from the environment onto the image plane (note, they will be inverted). If a lens is involved (as in vertebrate eyes and real cameras), then more light can get in, but at the price of being focused; only objects a particular range of distances from the lens will be in focus. This range of distances is called the camera’s depth of field.

 

The image plane is usually subdivided into equal parts, called pixels, typically arranged in a rectangular grid. In a typical camera there are 512 by 512 pixels on the image plane (for comparison, there are 120 x 10^6 rods and 6 x 10^6 cones in the eye, arranged hexagonally). Let’s call the projection on the image plane the image.

 

The brightness of each pixel in the image is proportional to the amount of light directed toward the camera by the surface patch of the object that projects to that pixel. (This of course depends on the reflectance properties of the surface patch, the position and distribution of the light sources in the environment, and the amount of light reflected from other objects in the scene onto the surface patch.) As it turns out, brightness of a patch depends on two kinds of reflections, one being specular (off the surface, as we saw before), and the other being diffuse (light that penetrates into the object, is absorbed, and then re-emitted). To correctly model light reflection, as well as reconstruct the scene, all these properties are necessary.

 

Let us suppose that we are dealing with a black and white camera with a 512 x 512 pixel image plane. Now we have an image, which is a collection of those pixels, each of which is an intensity between white and black. To find an object in that image (if there is one, we of course don’t know a priori), the typical first step (”early vision”) is to do edge detection, i.e., find all the edges. How do we recognize them? We define edges as curves in the image plane across which there is significant change in the brightness.

 

A simple approach would be to look for sharp brightness changes by differentiating the image and look for areas where the magnitude of the derivative is large. This almost works, but unfortunately it produces all sorts of spurious peaks, i.e., noise. Also, we cannot inherently distinguish changes in intensities due to shadows from those due to physical objects. But let’s forget that for now and think about noise. How do we deal with noise?

 

We do smoothing, i.e., we apply a mathematical procedure called convolution, which finds and eliminates the isolated peaks. Convolution, in effect, applies a filter to the image. In fact, in order to find arbitrary edges in the image, we need to convolve the image with many filters with different orientations. Fortunately, the relatively complicated mathematics involved in edge detection has been well studied, and by now there are standard and preferred approaches to edge detection.

 

Once we have edges, the next thing to do is try to find objects among all those edges. Segmentation is the process of dividing up or organizing the image into parts that correspond to continuous objects. But how do we know which lines correspond to which objects, and what makes an object? There are several cues we can use to detect objects:

 

We can have stored models of line-drawings of objects (from many possible angles, and at many different possible scales!), and then compare those with all possible combinations of edges in the image. Notice that this is a very computationally intensive and expensive process. This general approach, which has been studied extensively, is called model-based vision.

 

We can take advantage of motion. If we look at an image at two consecutive time-steps, and we move the camera in between, each continuous solid objects (which obeys physical laws) will move as one, i.e., its brightness properties will be conserved. This hives us a hint for finding objects, by subtracting two images from each other. But notice that this also depends on knowing well how we moved the camera relative to the scene (direction, distance), and that nothing was moving in the scene at the time. This general approach, which has also been studied extensively, is called motion vision.

 

We can use stereo (i.e., binocular stereopsis, two eyes/cameras/points of view). Just like with motion vision above, but without having to actually move, we get two images, which we can subtract from each other, if we know what the disparity between them should be, i.e., if we know how the two cameras are organized/positioned relative to each other.

 

We can use texture. Patches that have uniform texture are consistent, and have almost identical brightness, so we can assume they come from the same object. By extracting those we can get a hint about what parts may belong to the same object in the scene.

 

We can also use shading and contours in a similar fashion. And there are many other methods, involving object shape and projective invariants, etc.

 

Note that all of the above strategies are employed in biological vision. It’s hard to recognize unexpected objects or totally novel ones (because we don’t have the models at all, or not at the ready). Movement helps catch our attention. Stereo, i.e., two eyes, is critical, and all carnivores use it (they have two eyes pointing in the same direction, unlike herbivores). The brain does an excellent job of quickly extracting the information we need for the scene.

 

Machine vision has the same task of doing real-time vision. But this is, as we have seen, a very difficult task. Often, an alternative to trying to do all of the steps above in order to do object recognition, it is possible to simplify the vision problem in various ways:

 

Use color; look for specifically and uniquely colored objects, and recognize them that way (such as stop signs, for example)

 

Use a small image plane; instead of a full 512 x 512 pixel array, we can reduce our view to much less, for example just a line (that’s called a linear CCD). Of course there is much less information in the image, but if we are clever, and know what to expect, we can process what we see quickly and usefully.

 

Use other, simpler and faster, sensors, and combine those with vision. For example, IR cameras isolate people by body-temperature. Grippers allow us to touch and move objects, after which we can be sure they exist.

 

Use information about the environment; if you know you will be driving on the road which has white lines, look specifically for those lines at the right places in the image. This is how first and still fastest road and highway robotic driving is done.

 

Those and many other clever techniques have to be employed when we consider how important it is to “see” in real-time. Consider highway driving as an important and growing application of robotics and AI. Everything is moving so quickly, that the system must perceive and act in time to react protectively and safely, as well as intelligently.

 

Now that you know how complex vision is, you can see why it was not used on the first robots, and it is still not used for all applications, and definitely not on simple robots. A robot can be extremely useful without vision, but some tasks demand it. As always, it is critical to think about the proper match between the robot’s sensors and the task.

 

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