N. Fowleri Diagnosis, Treatment and Prevention

N. Fowleri Diagnosis, Treatment and Prevention Historical Aspect: Naegleria Fowleri (N. Fowleri ) is a free living, thermophilic protozoan that is a human specific pathogen that attacks the central nervous system. It can be found in contaminated freshwater sources. It enters through the nose and travels to the brain causing primary amoebic meningoencephalitis1. It was first observed in 1899 and later named after Dr. M. Fowler, who observed the first reported fatal cases of acute pyogenic meningitis in Australia in 19652. While these infections have been identified as early as the 19th century it is challenging to identify because it mimics many of the symptoms of bacterial meningitis[1]. Primary amoebic meningoencephalitis (PAM) is a necrotizing and hemorrhagic meningoencephalitis3. The symptoms begin 1-9 days after the onset of infection these symptoms include fever, nausea, headache and vomiting. The initial symptoms mimic those of bacterial meningitis, the later symptoms are unique to this disease. Later symptoms include neck stiffness, hallucinations, seizures, an inability to focus, lack of balance and eventually coma and death. The mortality rate for this disease is 95%. The disease progresses quickly and leads to death within 12 days of the initial infection1. While this infection has a high mortality rate, it is very rare. There have been 300 reported cases of PAM worldwide in the last 40 years4. It is important to note that this conditioned is often misdiagnosed so these numbers are estimates. In the United States there have been 138 cases in the last 50 years1. This infection was once a condition that plagued developing countries but the incidence is spreading all over the world. Researchers suspect that the increased temperatures due to global warming, increased use of public water sources due to scarcity and an overall increase in aquatic recreational activities are to blame3,18. While swimming and other aquatic recreational activities help proliferate this disease so do rituals. Aga Khan University in Pakistan noticed an increased number of deaths caused by PAM in young males that had no history of swimming, but were devout Muslims. Those who practice this faith pray five times a day and before every prayer, they perform ablution, ablution is the washing of the hands, face, ears, nose, mouth, arms and feet. While cleansing the nose, water is forced up the nose putting individuals performing this practice with inadequately purified water at a greater risk for PAM3. Religious festivals like the Kumbh Mela where Hindus gather and swim in the Ganges river put those who participate at risk of developing diseases like PAM caused by N. Fowleri 3. In addition to religious practices, therapeutic interventions like the Neti pot increase the risk of PAM. Nasal irrigation systems like the Neti pot work to relieve the symptoms of sinusitis and cold. It works by removing debris and mucus from the nasal passages. The recommendation is that the water should be boiled or mixed with a non-ionized sodium chloride. Basic structure: N. Fowleri are a part of the free living amoeba that cause infections in the central nervous system. Some of the other protists are Acanthamoeba spp and Balamuthia mandrillas. Naegleria fowleri have been classified by modern techniques which analyze morphology, biochemical pathway and molecular phylogeny2. The modern approach classifies N. Fowleri as a part of the super group Excavata, in the group Heterolobosea and a part of the family Vahlkampfiidae. Although the genome for N. Fowleri is not yet completed there are some studies producing information about its molecular and genetic characteristics. N. Fowleri s genus includes more than 40 species, but N. Fowleri is the only one that is known to cause disease in humans. De Jonckheere created the most popular identification system for N. Fowleri . The identification system uses genetic markers like internal transcribed spacers (ITS1) and 5.8S rDNA 2. This identification system revealed at least 8 different genotypes. The genotypes are dispersed among different continents America (I,II,III), Europe (III,IV,V,VI,VIII), Oceania (V), and Asia (II,III). Of the eight genotypes only four have been found in humans, types 1-42. Naegleria are a part of the group heteroloboseans that have a three-phased lifecycle. They are first amoeba, then flagellate and lastly cyst formation5. N. Fowleri reproduces in the amoeba form via binary fission to produce the cyst and the flagellate forms. The entire cell cycle is 8 hours, N. Fowleri spends 28 minutes in M phase, 180 minutes in G1, 183 minutes in S phase, and 90 minutes in G22. In the amoeba form, the trophozoite ranges in size from 15-25 Â µm. Trophozoites also have cytoplasmic projections called food cups which allow phagocytosis of bacteria, yeast, erythrocytes and cellular waste. Trophozoites are the form of the amoeba that can feed and divide, they are also the form that enter the human host6.Trophozoites will transition into the flagellate stage after being exposed to a saline solution2. The flagellates cannot feed or divide, the transition also involves a change in shape from pleomorphic to pear shaped with a pair of flagella. The flagella have the typical 9+2 structure and are surrounded by a cytoplasmic membrane. The 9+2 flagella structure describes the cross- sectional arrangement of microtubules that make up the flagella. There are nine doublet outer tubules and two central singlet tubules7. The cyst form is resistant to most disinfection. The cyst formation is spherical, smooth, double walled and refractive. They measure about 20Â µm. The material of the cyst wall is synthesized and packaged by the rough endoplasmic reticulum2. Route of Transmission: N. Fowleri is a thermophilic amoeba, its optimal temperature ranges from 1150 to 1220 F. N. Fowleri can typically be found in warm freshwater like lakes and rivers, warm water from industrial parks, or inadequately chemically treated water, other warm water sources like water heaters and soil. In their natural environment N.Fowleri phagocytize cyanobacteria and eubacteria to regulate levels. Samples from the lakes of the southern United States reveal that N. Fowleri introphozoite formis present during the summer. During the winter months N. Fowleri in cyst form survive in freshwater sources, but no form of N. Fowleri can withstand freezing temperatures1 . Most cases of PAM are caused by swimming in warm freshwater, from drinking water, recreational activities, ritual abulation and sinus irrigation systems1. Infection occurs when water containing N. Fowleri gets into the nose. The amoeba enters the nose and travels along the olfactory nerve, through a bony plate in the skull called the cribriform plate3. Once it reaches the brain it causes meningoencephalitis, cerebral edema and results in herniation. The olfactory bulbs and orbitofrontal cortices become necrotic and hemorrhagic. The data on both humans and mice support the conclusion that death is ultimately caused by increased intracranial pressure and herniation3. Swimming in water containing N. Fowleri increases the risk for PAM but age and sex are also risk factors. From the 1962- 2015 there have been 138 reported cases of PAM in the United States, 114 of the cases have been children around the age of 12. Nearly 75% of the infections have affected males1. Certain behaviors are associated with an increased risk of infection, those infected individuals reported participating in water related activities like swimming, diving and head dunking1. Although N. Fowleri can be transmitted through water it cannot be transmitted through aerosols or droplets, or via person to person contact. N. Fowleri can be found in other organs of the body, such as the heart, lung, spleen and thyroid1. Pathogenesis: N. Fowleri enter the human host through the nose which provides access to the brain. Within eight hours of infection N. Fowleri is present in the mucus layer of the olfactory epithelium. Within 24 hours N. Fowleri are in the olfactory bulb and present in the cribriform plate. By 96 hours neutrophil polymorphs cause a severe inflammatory response in the olfactory bulb which leads to brain tissue damage3. Contact dependent mechanisms are N. Fowleri mediated pathogenic processes. The primary mechanism of pathogenesis in N. Fowleri is adhesion. Adhesion allows for movement and chemotaxis in the nasal mucosa and assists N. Fowleri with disease progression. Adhesins are expressed on the surface of N. Fowleri, the adhesins are integrin like proteins surrounded by adhesion like structures. Fibronectin binding protein, protein kinase C and NFa1 are important to interrupting the host mediated cytotoxicity3. In an experiment testing cytopathicity of N. Fowleri, a culture would bind to Fibronectin and in the presence protein kinase C the ability of the amoeba to adhere increased8. N. Fowleri also produces Reactive Oxygen Species (ROS) which damage the host cell. Following cell damage, N. Fowleri uses phagocytosis and amoebastomes to assist N. Fowleri in breaking down and consuming the cells through a sucker structure on its surface. These processes are mediated via actin and involve the polymer ization of monomeric G-actin and filamentous F-actin. Studies have found that a membrane protein Mp2CL5 may also play a role in pathogenicity, without this protein N.Fowleri are nonpathogenic3 .This protein is suspected to aid in pathogenicity by navigating the environment, and movement toward food sources9. In addition to contact dependent mechanisms of pathogenicity, N.Fowleri also utilizes contact independent mechanisms. N-PFP is a cytolytic pore forming protein that depolarizes the cell membrane and decreases the integrity. Naegleriapores A and B are pore forming polypeptides that are very similar in structure and function. Both are antimicrobial and cytolytic polypeptides3. The enzymes phospholipase A, A 2 and C are present in patients with PAM. Phospholipases are responsible for the demyelination of white matter. Sphingomyelinase, neuroaminidase, elastase and proteolytic enzymes are responsible for demyelinating nerve tissue. N. Fowleri are hemolytic due to the heat shock protein 70 which is unaffected by salt concentrations, chelating agents, pH and temperature extremes3,10. This protein is present in the cytoplasm, pseudopodia and phagocytic food cups. There are many other factors associated with the pathogenicity of N. Fowleri and others that are suspected to have an effect on t he pathogenicity. On the onset of infection the hosts innate immune system attempts to reduce the pathogens cytotoxicity. During the early infection the body releases mucin which surrounds the N.Fowleri trophozoites to prevent cytotoxicity. In the later infection eosinophils and neutrophils surround the N. Fowleri cells to prevent cytotoxicity. Inflammation increases over time, although there are not many cells that penetrate the host epithelium. The inflammation and polymorph nuclear cells from the host response damage cerebral tissue2 . Diagnosis, Treatment, Prevention: Diagnosis of N. Fowleri is heavily dependent on laboratory techniques. The most effective way to diagnose N. Fowleri requires cerebrospinal fluid (csf) which is conducted while the patient is living and brain biopsy which is conducted post-mortem11. Different laboratory tests are utilized to analyze the specimen. When PAM is suspected, samples can be wet mounted and placed under a microscope to identify trophozoites12. Polymerase chain reaction is a method that can be used to amplify DNA, to identify the presence of N. Fowleri DNA in a sample11. Another laboratory technique involves antigens that were developed from mouse monoclonal antibodies (mAbs) against N. Fowleri . When indirect immunofluorescence assays are used mAbs react to N.Fowleri from specific geographic regions13. The infection due to PAM progresses quickly and as previously stated, mimics symptoms of bacterial meningitis. Even with the advances in laboratory diagnostics most cases are diagnosed post mortem making effective treatment elusive. One successful case study provides an example of effective diagnosis and treatment of this condition. On July 13, 2013, a 12 year-old girl presented to Arkansas Childrens Hospital vomiting, having trouble holding up her head and was unable to open her eyes. A few days prior to hospitalization the patient had been playing in a local water park. During her hospitalization she experienced hallucinations, and thirst. A spinal tap was performed which ruled out bacterial meningitis. The laboratory identified N. Fowleri trophozoites in the patients cerebrospinal fluid. After determining the infection was PAM caused by N. Fowleri, physicians initially treated the patient with antibiotics and antifungals like Amphotericin B, Rifampin, Fluconazole, Dexamethasone an d Azithromycin .None of these treatments improved the condition of the patient. The hospital petitioned the Center for Disease Control (CDC) to allow the use of a new experimental drug available for the treatment of N.Fowleri14. The drug Miltesfosine was given 36 hours after the initial diagnosis, physicians also lowered the patients body temperature to 93.2 F0 to reduce cerebral edema and intracranial pressure. After 18 days in the ICU there was no N. Fowleri found in her system. The patient experienced a full but gradual recovery over the next fifty five days. After seven days the patient was able to write her name, in fourteen days she was able to speak in one and two syllable words. She also underwent both speech and physical therapy14. This patient is one of the three known survivors of PAM. While the virulence factors and the degree of recovery that surround the other two cases of survival are unknown. The prompt diagnosis, treatment with Miltesfosine within thirty six hours and maintaining a low body temperature for this patient played significant roles in effectively treating this infection14. Although the first case of N. Fowleri was over 50 years ago, the mortality rate for this disease continues to increase due to water scarcity which increases use of water from public sources. As previously stated this condition is either diagnosed post mortem or misdiagnosed. The development of a standard microbial treatment will aid in the reduction of high mortality rates14. In the three cases of survival the patients were all intially treated with amphotericin B, rifampcin, fluconazole, dexamethasone and phenytoin during the first week of infection15. In 1969 a patient survived PAM with the successful treatment of amphotericin B. The patient in 2013 was initially treated with amphotericin B and it was ineffective. Miltesfosine effectively treated this patients PAM14. Other drugs with the potential to treat PAM have been tested, and some have been proven effective while others have not. Clotrimazole a drug that has been used as an antifungal had potential to treat PAM but under further study was deemed ineffective16. In developing countries like Pakistan where water is in short supply and ablution is common practice the danger of becoming infected with N. Fowleri is greatly increased. Water sources in these countries include wells or water storage tanks which are often contaminated with N. Fowleri 17. In order to prevent infection the World Health Organization (WHO) encourages that water storage units and wells be regularly tested to ensure proper disinfection. Public health organizations have also encouraged the use of nose clips while swimming in lakes and other freshwater sources, and boiling water that is used for ablution17. Chlorine disinfection regimens prevent against most pathogens in drinking water systems however free living amoeba like N. Fowleri survive most disinfection. The cyst form of N. Fowleri is resistant to most disinfection and are associated with biofilm that can build up in drinking water systems. N. Fowleri have been isolated in drinking water systems in Australia, the United States and Pakistan, in both Australia and the United States they maintain chlorine levels of 0.5mg/L at all times in the drinking water18.To test the amount of chlorine needed to eliminate N. Fowleri, researchers conducted an experiment using two separate sites, a pre re-chlorination site and a post re-chlorination site, both sites were monitored before and after re-chlorination for a year. The results were that after chlorination of greater than 1mg/L at each site, in the post re-chlorination site the amoeba were gone within 60 days. The pre re-chlorination site would have seasonal flares of N.Fowleri but the c hlorine levels eliminated the protozoan and prevented further spread. Overall chlorine levels above 1mg/L result in the elimination of N.Fowleri in drinking water systems18. Summary of current areas of research notes: N. Fowleri is a rare pathogen that was discovered over fifty years ago. Since its discovery still not much is known about this pathogen. Future research into this pathogen will focus on patient complaint diagnosis and treatment, expanding the drugs that are used, biomarkers, and drug targets. In order to determine whether the patient has contracted PAM due to N.Fowleri the patients csf is tested and if the test is negative for bacterial cultures and the patient has a history of swimming or other aquatic activities, then the patient tests positive for N.Fowleri. Extracting csf can increase the pressure in the patients brain and lead to herniation of the brain. Because N. Fowleri travels to the brain via the nasal passage, the proposed route of diagnosis is collecting a nasal sample. Research confirms that N.Fowleri can be collected in both csf and nasal cultures3. Drugs administered through the nasal cavity, through the transcribial route would be delivered across the cribifrom plate to the inferior portion of the frontal lobe. This is the site where N. Fowleri attacks and spreads to the central nervous system. Drugs like amphotericin B do not decrease the minimum inhibitory concentration (mic) when administered intravenously. By potentially administering the drug transcribialy, the drug passes the blood barrier which would allow the drug to be more potent, trail the route of N.Fowleri, attack the site of infection, allow the lethal dose of drug to achieve the mic without venous drainage, and lastly to avoid symptoms of intravenous drug administration 15. There are clinically approved drugs that have promising amoebicidal effects. These drugs interrupt the mechanisms and processes of the amoeba. Digoxin and proyclidine both exhibit amoebicidal properties. Digoxin treats atrial fibrillation and heart rhythm disorder by helping the heart beat stronger and with more rhythm19. Proyclidine is used to treat Parkinsons and other diseases that cause involuntary muscle movement20. In order for further testing of the amoebicidal effects of these drugs to continue to be studied more drugs that have the potential to be amoebicidal must be identified and screened for tests to go from in vitro testing to in vivo testing. There has not been a lot of emphasis on finding drugs that treat N. Fowleri because the condition is rare and affects populations in the developing world. Biomarkers for PAM have been challenging to identify because little is known about N. Fowleris pathophysiology. Mass spectrometry, NMR and other tools of analysis are being utilized to identify biomarkers. Researchers are also making biochemical profiles of individuals in populations that contracted the disease against those who did not. These profiles will include information on the individuals age, gender, ethnicity and factors that predispose them to this condition3. This condition is rare and because of its rarity has been studied infrequently. With limited time and resources N.Fowleri is funded and studied less frequently than conditions that affect larger populations like Malaria or the Zika virus. The range of drugs used to treat patients with PAM is severely limited, researchers are developing drugs that would inhibit different processes of N.Fowleri. The drug pathways are hydrolytic enzymes that invade the host cells, glycocytic enzymes that are expressed differently by the pathogen, thiol based redox metabolism pathway, oxidative stress pathway, trypanothione pathways, and encystation and excystation pathways3. Bibliography 1. Naegleria fowleri- primary amebic meningoencephalitis (PAM) amebic encephalitis. Centers for Disease Control and Prevention Web site. =. Updated December 2015. Accessed January, 2017. 2. Martinez-Castillo M, Cardenas-Zuniga R, Coronado-Velazquez D, Debnath A, Serrano-Luna J, Shibayama M. Naegleria fowleri after 50 years: Is it a neglected pathogen? J Med Microbiol. 2016. doi: 10.1099/jmm.0.000303 [doi]. 3. Siddiqui R, Ali IKM, Cope JR, Khan NA. Biology and pathogenesis of naegleria fowleri. Acta Trop. 2016;164:375-394. doi: http://dx.doi.org/10.1016/j.actatropica.2016.09.009. 4. Coupat-Goutaland B, RÃ ©goudis E, Besseyrias M, et al. Population Structure in Naegleria fowleri as Revealed by Microsatellite Markers. Chiang T-Y, ed. PLoS ONE. 2016;11(4):e0152434. doi:10.1371/journal.pone.0152434. 5. The genome of naegleria gruberi illuminates early eukaryotic versatility. Cell. (- 5):- 631. doi: 10.1016/j.cell.2010.01.032. 6. Marciano-Cabral F, Cabral GA. The immune response to naegleria fowleri amebae and pathogenesis of infection. FEMS Immunology Medical Microbiology. 2007;51(2):243-259. doi: 10.1111/j.1574-695X.2007.00332.x. 7. Lodish H, Berk A, Zipursky SL, et al. Molecular Cell Biology. 4th edition. New York: W. H. Freeman; 2000. Section 19.4, Cilia and Flagella: Structure and Movement. Available from: https://www.ncbi.nlm.nih.gov/books/NBK21698/ 8. Han, KL., Lee, HJ., Shin, M.H. et al. Parasitol Res (2004) 94: 53. doi:10.1007/s00436-004-1158-9 9. RÉVEILLER FL, SUH S, SULLIVAN K, CABANES P, MARCIANO-CABRAL F. Isolation of a unique membrane protein from naegleria fowleri. J Eukaryot Microbiol. 2001;48(6):676-682. doi: 10.1111/j.1550-7408.2001.tb00208.x. 10. Song, KJ., Song, KH., Kim, JH. et al. Parasitol Res (2008) 103: 313. doi:10.1007/s00436-008-0972-x 11. Cope JR, Ali IK. Primary amebic meningoencephalitis: What have we learned in the last 5 years? Curr Infect Dis Rep. 2016;18(10):31-016-0539-4. doi: 10.1007/s11908-016-0539-4 [doi]. 12. Baig AM, Khan NA. Tackling infection owing to brain-eating amoeba. Acta Trop. 2015;142:86-88. doi: 10.1016/j.actatropica.2014.11.004 [doi]. 13. Pugh JJ, Levy RA. Naegleria fowleri: Diagnosis, pathophysiology of brain inflammation, and antimicrobial treatments. ACS Chem Neurosci. 2016;7(9):1178-1179. doi: 10.1021/acschemneuro.6b00232 [doi]. 14. Heggie TW, KÃ ¼pper T. Surviving naegleria fowleri infections: A successful case report and novel therapeutic approach. Travel Medicine and Infectious Disease. . doi: http://dx.doi.org/10.1016/j.tmaid.2016.12.005. 15. Baig AM, Khan NA. Novel chemotherapeutic strategies in the management of primary amoebic meningoencephalitis due to naegleria fowleri. CNS Neuroscience Therapeutics. 2014;20(3):289-290. doi: 10.1111/cns.12225. 16. Jamieson A. Effect of clotrimazole on naegleria fowleri. J Clin Pathol. 1975;28(6):446-449. 17. Siddiqui R, Khan NA. Primary amoebic meningoencephalitis caused by naegleria fowleri: An old enemy presenting new challenges. PLoS Negl Trop Dis. 2014;8(8):e3017. doi: 10.1371/journal.pntd.0003017 [doi]. 18. Miller HC, Morgan MJ, Wylie JT, et al. Elimination of naegleria fowleri from bulk water and biofilm in an operational drinking water distribution system. Water Res. 2016;110:15-26. doi: S0043-1354(16)30912-5 [pii]. 19. Dawson AH, Buckley NA. Digoxin. Medicine. 2016;44(3):158-159. doi: http://dx.doi.org.proxy.campbell.edu/10.1016/j.mpmed.2015.12.006. 20. Procyclidine. Drugs.com Know more. Be sure Web site. https://www.drugs.com/cdi/procyclidine.htm. Updated 2017. Accessed 5/25/17, 2017. [1] Naegleria fowleri- primary amebic meningoencephalitis (PAM) amebic encephalitis. Centers for Disease Control and Prevention Web site. https://www.cdc.gov/parasites/naegleria/pathogen.html#history. Updated December 2015. Accessed January, 2017

Shc34 – 2.1, 2.2 & 2.3

SHC34 – 2. 1, 2. 2 & 2. 3 Potential dilemma 1 – If a child in the setting is using their own language, religion and customs due to wishes of parents/family. Why is this a dilemma? This is a dilemma as the practitioners at the setting my not be able to understand the child, this means they will struggle to teach the child and help them develop. If the parent does not want the child to learn English it may be a problem, most of the school/setting will be speaking English.The parent may feel they are not focussing enough on this certain child's religion and also, since the child is using their own customs they may find some of ours offensive. The difficulty between my duty of care and the rights of the child – A practitioner would have a duty of care to educate the child and help them develop. The child has a right to use their own language, religion and customs of family or group, this means the practitioner could not stop the child from getting an education becaus e of their language, religion and customs, they have a right to this.Also, linking to this, the child has a right to an education, meaning you would have to provide this to the child under any circumstances. How would I deal with this situation? First of all, I would try to compromise with the parent, that the child could possibly speak English in the setting and speak their own language at home. Explain to the parent this may affect their holistic development and exactly what it will affect and how. This may be too big of a compromise, so if not I would look into getting a translator into the setting to help the child develop and learn.What could be the risks for the child? The risk here for the child is that they may not develop fully. This would be their holistic development as they will not be able to understand the practitioner when they are explaining activities and work. They will not be socialising and they may get frustrated and feel alone in the setting. Potential Dilemma 2 – If a member of the family turns up to pick a child up, one that is not supposed to due to wishes of parents/family. I will use mother as an example in this dilemma, if a mother is not allowed contact with the child. Why is this a dilemma?There is a risk of upsetting the child if they see the mother which really shouldn't happen as they should not be let in, although sometimes there could be a situation where the mother is forceful. The family member who has asked for the mother not to see the child could be upset by this, as it was against their wishes for the mother to try to contact them. The difficulty between my duty of care and the rights of the child – A practitioner would have a duty of care to protect the child, keep them safe and there had to be a reason for them not being allowed contact, they should also respect the parents/family's wishes.According to the UNCRC the child has a right for their family to be together, this means the child would normally ha ve a right to see a member of their family, but in this situation it is best not to go against the familys wishes despite that right. How would I deal with this situation? I would deal with this situation by letting the mother know that she is not permitted to enter the setting. I would explain there was no possible way she could take the child as there are certain people who are allowed to pick every child up and she is not down as one.I would ask the mother to leave the setting and if it did turn into a forceful situation I would call another member of staff to help escort this person out. If we could not get the parent to leave we would have to involve the authorities. What could be the risks for the child? The risks for this child could be a variety of different things. Without knowing the mothers background we couldn't say any specific risk as the mother could be dangerous or it could be other reasons.If the child see's this person they may get confused, they may not even recog nise them but if they do it may confuse them as they are not permanent in their life. Potential dilemma 3 – If you think a child in the setting may have a special educational need but the parent does not want them referred to find out as they do not believe the child has a special educational need. Why is this a dilemma? This is a dilemma as the child may not be able to develop properly if it is not clear if they do need extra support.They will also be sure how much support and what kind of support they need by finding out what special educational need they have. The difficulty between my duty of care and the rights of the child – As a practitioner I have a duty of care to make sure the child is developing as they should, I should be making sure the child is reaching their full potential. I would also have to respect the parents wishes. Every child with special needs should have special care and support, if the parent rejects this idea it will be very difficult to get support. How would I deal with this situation?I would try to explain to the parent how it would benefit the child to even talk to someone about their special educational need. I would explain as best I could that this was important for the child but I could also arrange something with the SENCO so they had all the information they needed to make the desicion. What could be the risks for the child? The risks in this dilemma for the child would be that they may not be developing hollistically, they would need extra support that they are not getting. This could affect the child later in life too as they may struggle in their education as they get older.It is always best to identify a special educational need at the earliest possible point as this benefits the child, they may start lacking in all area's of development the later it is left. Where to get support and advice – For certain situations it means different people to contact for support. SENCO, your manager, child protecti on officer, social services etc. These are a few people you could go to when conflicts or dilemma's arise as they may be able to support or advise you. They may be able to work beside you to get the best outome for the child and support/advise you throughout it. Danielle Le Vesconte 30105251 1578571749

Top Safety Patrol Essay Samples Guide!

Top Safety Patrol Essay Samples Guide! The Fight Against Safety Patrol Essay Samples Various courses of action is going to be taken dependent on the degree of threat involved. An improved safety training regime requires employees involved with blasting to wear an indicator showing their existing amount of training on their hard hat in any respect times. All this is based off of the very first program that was made by the Congress in 1968. Students and staff should be offered with training on how best to respond to a pure disaster. What's Really Happening with Safety Patrol Essay Samples They change lots of things to produce the ship stronger and more efficient. Every security worker utilizes some type of prop or tool. You never know who you are receiving in the auto with,'' Norred explained. The exact same applies to all mechanical facets of the aircraft, and satellite navigation systems, landing gear and a lot more. Hence it becomes quite important that everybody should strictly comply with the traffic rules and ought to always drive safely with respecting the other people and vehicles on the street. Most importantly, there's a demand for us to be worried about our own safety and conduct whilst using the road. In practice an individual can actually discover that there's no such thing as absolute safety. For example fire alarm drills are performed in most organizations in order to make sure that folks understand how to respond in the event of a fire. New Questions About Safety Patrol Essay Samples To assist you do that, here are a couple of tips. The secret to the success of a security and wellness program is to see it like part of the company operation and to see it reflected in the day-to-day operations. There are a number of education and certification bodies accountable for providing safety certificates, so it is necessary to choose which institution to attend to find the training. A security management plan comprises the general security procedures that are relevant to a firm. As a way to understand safety management, an individual must first demystify the notion of safety. Ensuring road safety is vital and have to be prioritized by the governments and individuals. To summarize, a perfect safety management system would incorporate a management program and safety promotion. Developing a security certificate from scratch isn't easy. A procedure is also like building a document, there's a step-by-step process regarding how you should format it. There's an application procedure that demands the student to compose a brief paragraph describing why they'd love to be on the team and obtain their parent's approval. Scanning The major idea behind scanning is to recognize the issue. The sample of school security plans included here is meant to provide you with an overall idea of strategies that could be implemented to shield students, teachers, and visitors ali ke. Furthermore, the write-up discusses the use of civilians in the procedure for preventing crime, which lowers the burden on the traditional police patrol. Safety can just be defined as a circumstance where there isn't any harm or danger. A statement about the school's social and cultural atmosphere. Conclusion Traffic accidents are a main cause of deaths in India and it has affected an enormous number of families. Accordingly, in conclusion, police patrols ought to be continued, and ought to be supported by communities if they are supposed to continue to properly function. Why Almost Everything You've Learned About Safety Patrol Essay Samples Is Wrong Just comply with the guidelines stated above, and you will be well on your way to writing an excellent persuasive essay. The value of research in persuasive writing cannot be overstated. You still must make an outstanding bit of writing. Keep reading to learn. Even when you're not likely to compose a paper about it, you may as well opt for a topic from the list of persuasive essay topics above that for sure will be great for you. Evidently, you ought not purposely choose a topic that will bore your audience. When you settle on the subject and select the position on which you will base your essay, the remainder of the job can then begin. Possessing great research abilities and selecting an excellent topic is important.

The different models of the biped walking robots. - Free Essay Example

Sample details Pages: 31 Words: 9206 Downloads: 1 Date added: 2017/06/26 Category Statistics Essay Did you like this example? INTRODUCTION AIMS AND OBJECTIIVES CHAPTER 3.LITERATURE REVIEW This portion would discuss the background research in detail, the methodologies and other useful aspects involved in designing the earlier models of the bipeds and pros and cons of the different models of the biped walking robots. The first biped walking robot was established in 1893 by a native Canadian; Prof. George Moore (Mechanical Man, 1893) reported he build a robot which was a figure of a man, constructed of iron and fitted with internal mechanism, used steam for motion was intended to move similar to the walking gait of a human being. I t appeared like an old-fashioned knight. The walking speed for this model was around four to five miles per hour and stood six feet tall in height. (Roshiem, 1994) stated that the steam man was powered by a gas fired boiler with a power of 0.5 h.p. Swing arm provided it with stability as it guided him in circles. Don’t waste time! Our writers will create an original "The different models of the biped walking robots." essay for you Create order (Machado, Silva, 2005) told that computer controlled biped systems has been a much focused area at Waseda University, Japan, since the end of 1960s. At the Humanoid Research Laboratory a biped robot was transpired by Ichiro Kato on 1969 which was called WAP-1. The robot mainly consisted of artificial rubber muscles for its actuation. Playback of priory taught movement was used for the biped locomotion. The main restraint in WAP-1 was its low speed. It was followed by WAP-2 and WAP-3. (Thomas Isaac, 2004) stated that in 1971 WAP-3 was developed which could not only move on flat surfaces but could also move up and down on the stair case by moving its center of gravity on the frontal plane. WAP-3 was the first in the world to achieve the three-dimensional walking and turning. It was directed by a control based memory. 3.1 WL-10RD, BIPER-3 and 4 As stated (Elliot Nicholls, 1998) in 1985 another robot used the quasi-dynamic walking which was named WL-10RD and it was developed by the same research team as above. Since this time the development in this research has been rather drippy. BIPER-3 was developed in 1984 by Miura and Shimuyana which completely flake out the static balance entirely. This was modeled after the human walking on stilts, showed true active balance. This robot contained three actuators in which one is used to change the angle separating the legs towards the motion direction and the other two which lifted the legs to the side in the sidelong plane. This robot is termed as three degree of freedom robot. Later another robot was developed named BIPER-4 and this was extended to seven degree of freedom robot. Another robot was developed by Raibert using the methodology that the robot used uncluttered driven leg for the leaping motion and was attached to a chain which restricted pitch motion, vertical and horizontal translation around a radial path inscribed by the chain. The current progress of the leaping motion of the robot was tracked using the state machine activated by the sensor feedback. The state machine was then used to modify the control algorithm which modified three parameters of leaping stride forward speed, foot placement and body attitude. Hodgins, Koechling and Raibert developed a dynamic running robot which extended the earlier study of one-legged hopping robot into two and three dimensional. The two dimensional robot used the same control methodology as previously used in the hopping robot in two- dimension controlling the three aspects of the running stride which are body height, foot placement and body attitude using the state machine. The robot was controlled differently using the different sates of the sate machine. 3.2 WHL-11 (Karsten Burns, 2010) describes that in 1985, biped walking robot was developed by Waseda Universitys Humanoid research laboratory in partnership with Hitachi Ltd. The robot could walk on flat path at the rate of 13 seconds a foot and it was achieved by putting an onboard computer and a hydraulic pump in addition to that of earlier WL series robot. It was seen that this robot could walk up to 64 km. The main cons in this robot were that it was unable to walk on inclined surfaces. So since the work is being done to stabilize the movement to develop a control system that can adjust gaits. 3.3 WL-12RIII Another biped walking robot was established in 1989 as described by (Agrosy 2010) named WL-12RIII and it used the principle of stabilizing its walking on different paths using the trunk motion. An algorithm was developed used to calculate trajectory of the trunk and was done by introducing a virtual surface which is derived from the geometry of the path and the trajectory of the feet. When experimented on a stair with a height of 10cm and the time it took to go up and down was 2.6 seconds and when experimented on a inclination of 10 degrees, it took 1.6 seconds to walk down the path. Kato came up with a control methodology where the path of the robot is unknown as well as the external forces acting on it by using combinational motion of the trunk and lower portion of the biped. So finally the step size of the biped was reduced to 0.64 of a second. 3.4 WASUBOT and Manny (Agrosy, 2010) has explained in his site that WASUBOT is another biped robot. Its basic principle is the same as that of the WABOT-2. The change was rather a clarification in maintenance of the robot and WAM 8s as the arms. In 1989 at Battelles Pacific Northwest Laboratories in Richand, a full manlike behavior robot named Manny was developed. It took three years and $2 million to develop this robot by the work of 12 researchers. It was delivered to the US Armys Dugway proving ground in Utah. Manny had 42 degree of freedom. 3.5 P1, P2 and P3 According to (Daniel Ichbiah 2005) with the aim of producing bipedal walking robots in 1993 the first series of P prototypes came into existence. First developed was P1 which was quite big and heavy like a metal monster which was 6 feet and 2 inches in height and was 175 kilograms in weight. Instead of a face it had a big screen of rectangular shape. In challenge of making robots more or less like the humans they came up with others models like P2 and P3. P2 came into being officially on 20th of September 1996 and cost around $ 105.3 million. It was shorter in height but weighed more like 208 kilos. September marked a critical moment in the history of Biped robots by the coming of P3. It was made of purified white steel and plastic and resembles to an astronaut. It was based on the same technological model and had same technological capabilities but its height was 5 feet and 4 inches and weighed 130 kilos quite short and light weighted as compared to the earlier models. P3 walked at the same speed as the human. Coming of P3 was a big step towards the modelling of Biped robots quite similar to humans. Honda was keen to accept this challenge of reducing some more weight. In 2003 an upgraded version of Asimo was introduced it was a great machine which had some social ethics of greeting. It could also pass information like the weather forecast. According to (Daniel Ichbiah, 2005), in the summer of 2003 HPR-2 came in to existence by the production team of AIST. It was a prototype which could get down and stand up all by itself. It worked using the limb coordination software and Kawada industries were able to design its body with flexible joints but the main problem was it was heavier and taller than Asimo. (Kieth Kleiner, 2009) told that Toyota in 2009 developed a humanoid robot which could run upto 7 km/h overcoming Hondas Asimo which could run to 6 km/h. Hondo Asimo robot is capable of ascending and descending on a staircase and handling varying circumstances unlike Toyota which can only on flat surfaces. (Kim Tae Gyu, 2009) Humanoid robot RX is a running robot which was developed by South Korea which after Japan is the second in the world which was put forward by a local avocation working with not much of a budget 3.6 Main point according Fumio Kanehiro According to (Daniel Ichbiah 2005) Fumio Kanehiro who is the member ASIT said One of the main problems with humanoid robots is that they easily fall over. When a biped robot stands on its two feet, only a very small area in contact with the ground supports it, while its centre of gravity is at waist level, which is relatively high. Year Researcher Area of Development 1850 Chebyshev Design Linkage used in early walking mechanism 1872 Muybridge Uses stop motion photography to document running animals 1893 Rygg 1961 Space General Eight legged kinematic machine walks in outdoor terrain 1968 Frank and McGhee Simple digital logic controls walking of Phony Pony 1977 McMahon and Greene Human runner with speed record on tuned track at Harvard 1980 Kato Hydraulic biped walks with quasi-dynamic gait 1981 Miura and Shimoyama Walking biped balances actively in three-dimensional space 1985 A. Takanishi et al Realization of dynamicbipedwalking stabilized with trunk motion under known external force 1992 Kajita et al Dynamic Walking Control of aBiped RobotAlong a Potential Energy Conserving Orbit 1996 Kun, A., Miller II daptive dynamic balance of abipedusing neural networks 1998 Park, JH and Rhee ZMP trajectory generation for reduced trunk motions ofbiped robots 2000 elexistence technology was adapted in a new type of cockpit system to control a humanoid biped robot 2002 S. Meyret, A. Muller Adaptative neuro-fuzzy control of the rabbitbiped robot 2004 J. Gutman, M. Fukuchi Detection of stair dimensions for the path planning ofbiped robot 2006 A. Sutherland Torso Driven Walking Algorithm for Dynamically Balanced Variable SpeedBiped Robots 2007 F. Asano and Z.W. Luo Asymptotically stable gait generation forbiped robotbased on mechanical energy balance Table. Development in the field of legged robots CHAPTER 4 BIPEDAL WALKING 4.1 Why Study Legged Robots? (M.H Raibert 1986) mentioned there is a contemplative reason for researching robots with legs, apart from the outright adventure of developing robots that can actually run. Reason being the mobility and they provide an exertive suspension from the gait of the feet. Moving through difficult terrain, where other cannot go is one of the main reasons for legged robots. Legged robot perform actively while moving on a rough terrain unlike the traditional wheeled robots which can only move on flatter surfaces and in result this limits the wheeled robots to move on half the earths landmass. Legged robots use isolated footholds that maximise support and friction but wheeled robots need a constant path of support. Another advantage is, despite pronounced variations in the terrain, the payload is free to travel stably. Legged robots can also tip through the hurdled obstacles. (Yang and Kim, 1998;; Spenneberg, et al., 2004) have investigated a further lately, worries malfunction tolerance during immobile stable locomotion. The effect of a failure in one of the wheels of a wheeled vehicle is a stern lost of mobility, since all wheels of these kinds of vehicles should be in permanent contact with the ground during locomotion. However, legged vehicles may present a superfluous number of legs and, therefore, can maintain static balance and continue its locomotion even with one or more of its legs damaged. (M.H Raibert 1986) explains another main reason for studying legged robots is to boost a greater knowledge of human and animal movement. This point could further be explained by actually analyzing the athletes during the instant replays. We could analyze the complexities and the various procedures involved in the various postures and position of legs while they are performing different tasks and can study the movements while they swing, throw, drift, maintaining balance and speed as they go or otherwise drive their body through space. This performance can not only be seen in the athletes performing on Television we can have our sight set at the local playground where ones own child in coming forward from a phase of crawling on four sets to walking on two legs and then running, jumping, climbing and performing various other exercises. 4.2 Walking Gait Studying and analysing (M.W.Whittle, 2003) normal gait has quiet an importance. It is also important to know the nomenclature used to describe the gait. This section gives a detailed overview of the gait cycle before formally developing a detailed mathematical and software model. It is challenging (Joel, DeLisa, 1998) to come up with a formal definition of the walking gait without sounding pompous as it looks quite a simple task. An informal definition of the walking can be put forward as a method of locomotion involving the use of two legs, to provide both support and propulsion. Clinical study of the gait is the most commonly used technique from the various techniques. A single gait cycle can be described as the sequence or interval between a foot strikes to foot strike of the same leg. There have been (Lamm R.D., 1995) two main classifications of a complete gait cycle phase: stance phase and the swing phase. The phases are also subdivided as shown in the figure below. right left left right right left initial pre initial pre initial pre contact swing contact swing contact swing Time percent of cycle Double R.Single Support Double L.Single SupportDouble Support Support Support 0% 15% 45% 60% 100% 0% 40% 55% 85% 100% The interval of the stance phase is taken as 60% of the total interval. Double support phase and single support phase are the two sub-divisions of the stance phase. Double support phase can be encompassed as when both the legs are in contact with the ground. It has been analysed that at average walking the double support is 10% of the total gait interval, but as the speed increases, the double support interval decreases. The remaining interval is the single support phase. To avoid buckling of the support foot in the stance phase, the muscles like tibialis anterior, the quadriceps, the hamstring, the hip abductors come into function Energy conservation during a walking cycle can be categorized into three main events. The events include controlling the forward movement during the deceleration towards the end of the swing phase, jolt absorption while the foot land on the ground and momentum during push-off when the centre of gravity is pushed up and forward. A humans centre of mass is a located at the hip joint. Centre of mass does not deviate up or down, when a body is moving in a straight line, at his moment not much energy is required. This straight line is only possible wheels are placed instead of the feet, but this is not the case in humans so it deviates in a vertical and lateral sinusoidal displacement. At midpoint centre of mass is at the highest position and centre of mass during human locomotion goes in rhythmic flow of upwards and downwards motion. At time of the double support phase the centre of mass is at the lowest point 4.3 Why pointed feet? (Westervelt et al, 2007) degree of actuation of the system is an essential source of complication or in a more absolute domain, the degree under-actuation. Under-actuation is used to describe devices that have lower number of actuators then degree of freedom. Inverted pendulum is a classic example of under actuated system. The model taken in this report assumes that at stance leg there is no possibility of actuation and legs are terminated in points. There could be a major concern over modelling feet pointed because real robots have feet. Against the mechanical bipedal walking which is to be contrasted, if one takes a persons walking as the defected benchmark, then the flat-footed walking accomplished by current robots needs to be improved? In particular, toe roll toward the finish of the single support phase needs to be certified as part of the gait plan. Currently, this is not legitimate specifically because it leads to under-actuation, which cannot be indulged with the control des ign philosophy based on trajectory tracking and a quasi-static stability principle, such as the zero moment point (ZMP). A model of an anthropomorphic walking gait should at minimum regarded as a fully actuated phase where the stance foot is level on the ground, pursued by an under-actuated phase where the stance heel rises from the ground and the stance foot rotates with reference to the toe, and a double support phase where leg switch over takes place, optionally, heel strike and heel roll could also be incorporated, which would yield a second under-actuated phase in the gait. In either case, a model of walking with a point contact is an essential element of a general model of walking that is more anthropomorphic in nature than the existing flat-footed walking paradigm. Because of the fact that the model with point feet is quite simple as compared to a more complete anthropomorphic gait model, it makes possible the development of new feedback designs and dynamic stability analysis methods that are suitable for moving past quasi-static walking. 4.4 Terminology Some basic nomenclature would be put forward before going towards the formal mathematical modelling of the biped robot. This nomenclature would permit a casual explanation of the essential fundamentals of a dynamic model of a bipedal robot to be given which, in turn, will allow some demanding characteristics of the control problem to be elevated. A biped is referred to as an open kinematic chain which consists of two sub-chains which could be referred to as legs and torso. These are all connected at a common point called a hip. During the walking cycle of the biped, either one foot or both foot are on the ground. These are referred to as single support phase and double support phase. According to the model taken in this report, single support phase is defined as the phase of the walking cycle when only one foot is in contact with the ground. Stance leg is the contacting leg and the other is called the swing leg. When both feet are in contact with the ground, this is referred to as t he double support phase It is required that the movement of the robots centre of mass is strictly monotonic. Non-slipping nature of the feet is assumed when in contact with the ground. A planar biped is a biped whose motions only take place in the sagittal plane. Sagittal plane is the longitudinal planes that divide the body into right and left sections. Three dimensional bipeds have locomotion both in sagittal and frontal plane. A statically stable gait is a rhythmic movement in which the centre of the mass of the biped lies in the support polygon. All the point of contact on the ground forms a convex hull which is referred to as support polygon. A dynamically stable gait is a rhythmic movement where the centre of pressure of the biped is on the boundary of the support polygon for at least part of the cycle. 4.5Passive Dynamic Walking Passive dynamic walking is purely stationed on the recovery of the biped dynamic structure. Passive walkers are capable of maintaining a stable, rhythmic walking motion but they do not need external energy. The passive dynamic walker uses one leg to freely swing using its own weight and the other one supporting the swing. The second leg turns to swing while weight moves foot to another. The subject has been studied widely. (T. McGeer, 1990) showed that a biped robot, suitably constructed to walk without external support. Very little energy is required when the knee joints are used that is why people use walking to benefit the body and legs. (M. Coleman ja, 1998) purely passive walkers biggest limitation is their ability to walk only downhill. Increasing the systems low-power control can be achieved walker who keeps a stable walking motion ina flat or slight uphill, but whose energy is close to the minimum. (Ted McGeer,1990) the practical enthusiasm for working on passive walking is, first, that it makes for mechanical simplicity and relatively high efficiency. Second, control of speed and direction is simplified when one doesnt have to worry about the details of generating the gait. Moreover, the simplicity of the machine promotes understanding. Consider an analogy with the development of powered flight: The Wrights put their initial efforts into studying gliders, as did their predecessors Cayley and Lilienthal. Once they had a reasonable grasp of dynamics and control, adding a power plant was a relatively minor modification. (In fact their engine wasnt very good for its day, but their other strengths led them to outstanding success.) As Ill explain, adding power to a passive walker involves a comparably minor modification. 4.6Robot Walking Hypothesis (Westervelt et al, 2007) a biped walking robot would be modelled based on the properties listed below. In order to ensure the robot satisfies these properties, a controller would be imposed. The robot consist of periodic phase of single support and double support Throughout the contact, the stance leg end acts as an ideal pivot, during the single support phase. The ratio of the horizontal component to the vertical component does not excel the coefficient of static friction. The vertical component of the ground reaction device is non-negative. There is no slip or rebounding of the swing leg, while the previous stance leg discharges without correspondence with the ground. With respect to the two legs, the motion is symmetric in steady state. In each step, the swing leg begins from strictly behind the stance leg and at impact is positioned in front of the stance leg. Walking takes place on level surface from left to the right 4.7 Dynamics Model The biped under consideration is a simple two foot robot to ensure the possibility of mathematical simulation. The model simulates the complete walking system. (Olli Haavisto et al, 2007) biped robot is a two-dimensional system with five links including a torso and two identical legs with knees. This model has been used by many researchers (Hardt et al, 1999; Juang, 2000) as it explains the walking motion of a biped robot quiet well. mo (xo, yo) ro lo r1 m1 l1 L R ML1 r2 R MR2 y m2 l2 L ML2 x FLx FRx FLy FRy The biped robot under consideration needs seven variables to describe the position in two-dimensional coordinate system which means that the robot has seven degrees of freedom. The coordinate (xo, yo) describe the position of the centre of the mass of the torso in a fixed position and being the angle of the torso with respect to the normal. L is the angle that the left thigh joint makes with respect to the torso and R is the joint angle of the right thigh with respect to the torso. L and R are the left and right knee joint angle with respect to the left and right thigh joint respectively. q = [xo, yo, , L, R, L, R]T (l0, l1, l2) denotes the link length of the torso, thigh and the shin respectively and (m0, m1, m2) denotes the masses. The links centre of the mass is located at a distance (r0, r1, r2) from the corresponding joint. External forces are used to model the walking plane that involves both the legs. The forces are in effect, when the leg touches the ground, to support the leg. The force is zeroed when the leg is not in contact with the ground or when the leg rises. F = [FLx, FRx, FLy, FRy]T The actual control signal for the model is the four moments, two of them actuated between torso and both the thighs and two are actuated at the knee joints. M = [ML1, MR1, ML2, MR2]T The two foot walking model used here has been studied in detail. (C. Chevallereau, 2003) developed a robot named RABBIT in which it was assumed that the when the swing foot hits the ground the other foot immediately rises into the air. All the walking stages have been described in this model but thelegwill always causea a steppedchange inthe systemmode and is calculatedseparately. 4.7.1 Lagrangian mechanics (David McMahon, 2008) by taking the difference between the kinetic and the potential energies, a function lagrangian can be constructed. It can be used to derive the equations of the motion and is an equivalent to the Newtonian method. The lagrangian is a fundamental concept which captures all the dynamics of the system and allows us to determine many useful properties such as averages and dynamic behaviours. (R.D. Gregg, 2011) a mechanical system with n-degree of freedoms with Q as the configuration space is described by elements (q, q) of tangent bundle (the space of configurations and their tangential velocities) TQ and Lagrangian function L : TQ R given in coordinates by Lq, q= Kq, q- V(q) = 12qTM(q)q- V(q) Kq, q = kinetic energy Vq = potential energy M(q) = generalized mass/inertia matrix By the least action principle, system integral curve necessarily satisfy the Euler Lagrange (E-L) equations ddtqL- qL= where n-dimensions vector contains the external joint torques. This system of second-order ordinary differential equations gives the dynamics for the actuated mechanism in phase space TQ. These equations have the special structure Mqq+ Cq, q+ Nq= Bu where n x n matrix C(q, q)contains the Coriolis/centrifugal terms, vector Nq= qVq contains the partial torques and n x n matrix B maps actuator input vector u Rm to joint torques = Bu Rn. 4.7.2 Ground Contact (Heikki, 2004) using a set of x, y points, ground surface can be modelled which are linked through straight lines. In order to make the next ground point as origin point to negative x direction of the leg tip new coordinate system is defined i.e.(x, y). Below figure shows that the position of the axis x is tangential to the ground whereas y equals the surface normal direction. y x y (x0, 0) Ft (xG, yG) x Fn Figure: The leg tip touches the ground in point (x0, 0)(grey) and penetrates it.The current position of the leg tip is (xG, yG)(black). Normal and tangential forces are applied to the leg tip when it touches the ground at the point(x, 0). In order that the situation is analogous to spring damper system, the output of the PD controller is used to calculate the normal force. Fn=-kyyG-byyG yG = current (negative) leg tip y coordinate ky = ground normal elastic constant by = normal damping ratio In order to prevent the leg sticking to the ground, only positive values would be taken for the normal force. In the tangential direction the force Ft acting is due to friction. Similar to the normal force calculation, PD controller is used to determine static friction force. The nominal value is the initial touching ground x0 Ft=-kxxG-x0-bxxG kx and bx = ground tangential properties If there is an exceeding required force than the maximum static friction force Ft,max=sFn s = static friction coefficient If the leg starts to slide than the tangential force is Ft=kFn k = kinetic friction coefficient The accumulated value of x0 is constantly set to the corresponding leg tip xG position throughout sliding. In order to attain the dynamic model input forces, the normal and tangential forces are needed to be projected to the original coordinate system (x, y) after these forces are computed. 4.7.3 Model Equations (Olli Haavisto, 2004) system status is determined by the generalised coordinates and their time derivative, coordinates with each consequent to a generalized power Fq = [Fxo, Fyo, F, FL, FR, FL, FR]T The generalised coordinated of the centre of mass of the thigh of the left and the right leg is denoted by (xL1, yL1) and (xR1, yR1) respectively. The coordinates of the centre of the mass of the left and right shin link is represented by (xL2, yL2) and (xR2, yL2) respectively. The leg tip position of the left and right leg is denoted by (xLG, yLG) and (xRG, yRG) respectively. These notations can be represented in equations as: xL1= x0- r0sin- r1sin(-L) yL1= y0-r0cos-r1cos(-L) xL2= x0- r0sin- l1sin(-L)-r2sin(-L+L) yL2= y0- r0cos- l1cos(-L)-r2cos(-L+L) xLG= x0- r0sin- l1sin(-L)-l2sin(-L+L) yLG= y0- r0cos- l1cos(-L)-l2cos(-L+L) The kinetic energy can be easily expressed in terms of the Cartesian coordinates taking in to account all the links. The total kinetic energy can be written as T=12(m0x02+y02+m1xL12+yL12+yR12+yR12+m2xL22+yL22+yR22+yR22 The generalized forces in terms of generalized components can be written as Fx0=FLx+FRx Fy0=-m0+2m1+2m2g+FLy+FRy F=-yL1m1+yL2m2+yR1m1+yR2m2g+yLGFLy+yRGFRy+xLGFLx+xRGFRx FL=-yL1Lm1+yL2Lm2g+yLGLFLy+xLGLFLx+ML1 FL=-yL2Lm2g+yLGLFLy+xLGLFLx+ML2 For the right leg the coordinates will be replaced by the coordinates of the left leg and (FLx, FRx, FLy, FRy) as mentioned earlier are the external forces of both legs. Using the equation of the generalized coordinates, kinetic energy in terms of generalized coordinates and generalized forces are placed in the Lagrange equation and the dynamic equation can be written as Aqq= b(q, q, M, F) Using mathematica software this could be simplified, Aq R7x7 is the inertia matrix and b(q, q, M, F) R7x1 is the vector containing the right hand sides of the seven partial differential equations. Appendix B contains both A and b in closed form formulas. 4.7.4 Knee Angle limiter (Heikki, 2004), the knee angle limiter is set according to the ground surface. This is mainly done as same as the calculation for the ground contact normal force. A PD controller is used to control the maximum and the minimum limit of the knee angle. In order to prevent the joint rotating over or under the limit the controller output is added to the corresponding knee joint moment. It is desirable that the knee shouldnt rotate over or under the zero angle of L or R which is bending towards wrong direction. 4.8Control Model (R.K.Mittal et al, 2003) the control needs the data of the mathematical model and some kind of intelligence to proceed on the model. (Bijoy K. Ghosh, 1999) There are three functional abilities that a control design can be categorized to in which firstly being that at the task level the robotic system should be controlled directly i.e. without planning type decomposition to joint level commands, it should take task level commands directly. Secondly, rather than for a specific task, the robot control system should be designed for a large scale of tasks so the system becomes task independent. In the end robot should have the capability of handling some unexpected or uncertain events. A traditional control system is described in the figure shown below yd(s) e(s) y(t) s 4.8.1 PD Controller In modelling control for robots there is no compromise on the response time and the overshoot of a system because of the stability of the system. (Franklin et al, 2002) Proportional action provides an instantaneous response to the control error. This is useful for improving the response of a stable system but cannot control an unstable system by itself. Derivative action acts on the rate of change of the control error; this provides a fast response as opposed to the integral action. (G.C. Goodwin et al, 2001) proportional derivative control is essential for fast response self. Derivative controllers do not need a steady state error of zero. Proportional controllers are fast, derivatives controllers are also fast so combination makes very fast controller. (O. Haavisto, 2004) a discrete PD controller was developed in order to test the biped and get the system walking. The gait pattern formation is controlled by the walker with four separate discrete PD controllers, which are fed in order to change the reference signals. The left knee angle L and the right knee angle R provide their own separate controllers. The other controller controls the corner of the biped thighs i.e. difference of thigh angles = R-L. The fourth PD controller controls the torso angle , keeping the position of the torso upright. Knee angles controller provides control signals directly for the moments ML2 and MR2. The angle between the thighs = R-L, control signals have a positive effect on the right thigh torque MR1 and negative effect on the left thigh torque ML1. Both feet on the ground, influence the control signal evenly on the both thighs. The torso angle control was detached from the actual gait control so that it is feasible to decide the used angle separately. The control signal, however, needs to be added to the thigh moments. During the double support phase, the control signal is influencing both thigh moments, but during the single support phase only to the stance leg moment. System is used as the discrete PD controllers, whose transfer function has the form ukh= Pekh+Dhe(kh) k = sample number, h = sample interval e(kh) is calculated by subtracting the adjustable parameter reference value. The expression e(kh) can be directly obtained from current and previous signal value ekh=ekh-e(k-1h) By a suitable choice of the proportional controller gain P, the steady state error requirements can be met. 4.8.2 Reference Signals Signals are formed step by step adding, subtracting or keep references to constant values between the sampling systems status. References are constant at the beginning of the double support phase but when the momentum is shifted forward then the knee reference is increased the angle between the thighs is reduced when the foot is raised and system moves to change the phase. Swing leg is transferred front ways by reducing the angle between the thighs to a constant value, so that the foot does not hit the base too early. When the leg is swung forward the knee is straightened before the touchdown as it remains far from the base. The creation of the reference signals was planned so that the left leg is for all time the swinging leg. When a new double support phase begins, the left and right leg signals are in the state input and reference output switched. Below shows the table of the parameters used in the controller P D Double Support Phase: The angle between the thighs 60 1 Knee angle L, R 40 0,5 Torso angle 40 2 Phase Change: The angle between the thighs 70 6 Support leg knee angle 30 2 Swing leg knee angle 10 0,1 Table. PD-controllerused forwalkingdownthe parameters. CHAPTER 6 IMPLEMENTATION The biped walking model is implemented using Similink. The biped model in simulink consists of three blocks implementing dynamic equation of the biped model, calculating the ground support forces and limiting the knee angle. This model simulates complete walking model of the biped. The parameter definition of the biped model is shown in the table below. Field Description Units Robot dimensions: l Robot link length [l0, l1, l2] m r Centre of mass distances [r0, r1, r2] m m Link masses [m0, m1, m2] kg Robot initial state: coordinates [x0, y0, , L, R, L,R] m, (rad) speeds [x0, y0, , L, R, L, R] m/s, (rad/s) Knee angle limiter parameters: kk elastic constant Nm/(rad) bk damping ratio Nms/(rad) min minimum angle for L and R (rad) max maximum angle for L and R (rad) Ground Properties: ground surface points x1, x2, y1, y2, m ky normal elastic constant kg/s2 by normal damping ratio kg/s kx tangential elastic constant kg/s2 bx tangential damping ratio kg/s mus static friction coefficient s muk kinetic friction coefficient k Additional parameters: acceleration of gravity m/s2 sample time s These would be explained one by one in detail. 6.1 Biped block 6.1.1 Dynamic model This block output is a 14 x 1 matrix which calculates the position of the seven variables in which two are the position of the centre of the torso and five angles q = (x0, y0, , L, R, L, R) as described earlier and the rate of change of these variables q = (x0, y0, , L, R, L, R) after solving the equation q=bq, q, M, F*A-1(q) Inertia matrix A(q) is a 7 x 7 matrix and the complete formulas are shown in Appendix B. Matrix A depends on position of the seven variables. The matrix b is a 7 x 1 matrix and depends on 22 variables. The seven position variables q of the biped robot, their corresponding first derivatives q, the moments calculated from the PD controller and contact forces (two are used at a time because of one leg being in contact with the ground). 6.1.2 Ground Contact Model Ground support forces and the sensor values are the main output of this block. Initially the leg tip cartesian coordinates are determined using the formulae described earlier and the speed formulae are determined by taking the first derivative of the cartesian coordinates. The two identical control forces block handles the leg separately. This block calculates the tangential and normal forces by projecting the leg tip coordinate to the local (x, y) coordinate system and an in the end projects them to support forces. Sensor values tell whether the foot is in contact with the ground or not. When the leg is contact with the ground the sensor value is set to 1 and 0 otherwise. The senor value of the leg is determined by the relational operator as shown below in the figure. If the position of the leg tip is smaller or equal to the ground level that the relational will give a 1 on the output. 6.1.3 Knee Angle Limiter block If the angle of the joint does not remain in the given limits this block adds a moment value to the knee joint moments. The selector selects the position of the knee angles L and R and compares if the knee angle has gone beyond the maximum or minimum limit or not. The moments are added to the right and left knee moment and nothing is added to the other two moments. In this block if the knee angle goes over or under the limit than PD controller calculates the moment value and adds it to the previous values. 6.2 PD Control Block PDcontrolwas implementedin Simulinkblock,which istofeedthe systemstate, updatesiton the basis ofreference signalandcalculates thedifference variableon the basis of appropriatemoments.Figurebelowshowsblockstructurewhere thereferencesignals and theactualformation ofthe PD-controlisseparatedinto separate subsectors create references and controller Figure. PD controller block with create reference and controller sub block Figure below showstheCreatereferencesblockcontent.Reference signalis calculated assumingthat theswinglegisalwaysleftandrightleg.Therefore at the second stepthe signal of the biped must be changed. The reference creation is created using three main steps, as the there are two main phases in walking i.e. double support phase and the single support phase so the reference are created at these phases. There is another block in which the legs are switched as the controller is designed only for the left foot so when the leg strikes the ground the same process is switched to the other leg. If in the double support phase when the leg strikes the ground, difference between the horizontal distances i.e. xR x0 is more than 0.118 then the references block is enabled and references are calculated. The calculated step length error is subtracted from the horizontal distance of the robot. When the single support phase is enabled the references are created for the four controllers as described before. The Controller block initially determines the differences of the controlled variables and reference values. The constraints for the PD controllers are chosen in accordance with the phase of the step. After the control signals are calculated, they are changed to the moments. The four similar PD controllers take the difference signals and the parameters (P, D) as inputs and give the resultant control signals as outputs. The only special feature in the discrete PD controllers is the speed term zeroing. When the D parameter is transformed the speed term is zeroed for one time step in order to evade peaks in the output signal. Because all of the controlled variables cannot be affected straight through the inputs of the biped system, a conversion of the control values is needed. The control signal is separated to both thigh moments, and the torso angle control signal is added to the thigh moment of the leg that is touching the ground. If both legs are in contact with the ground, the control is divided equally between the two moments. CHAPTER 7 BIPED WALKING RESULTS In this section complete results of the walking of the bipedal would be discussed. As described earlier there are seven variables that mostly influence the biped robots x0, y0, , L, R, L, R. The position of these variables will be shown graphically and finally a complete walking cycle of the bipedal walking robot would be shown. A complete walking cycle was simulated and result were taken through the GUI The above figure shows a complete walking step of the biped robot, the dotted foot is taken as the left foot and the plain blue as the right leg. The left leg in this case is the swing leg and the right leg is the stance leg. The left foot take off from the ground and then takes a complete forward step and then gets back to the original position to become the stance leg and other one right becomes the swing leg. The horizontal coordinate of the centre of the mass of the torso will increase almost linearly with respect to time as shown in the graph. The y-axis shows the horizontal mass centre x0 w.r.t to x-axis and time on the x-axis The vertical movement of the centre of the would be similar to a projectile motion as the biped moves forward with time the centre of the torso will go upwards and then back down to the original position. The initial value for y0 is given in the m-file as 1.3749. There is a slight movement at the beginning that is because initially for some time there is a double support phase before the swinging of leg. In the figure shown below y-axis denotes the vertical position of the torsos centre and time on the x-axis. The angle which torso makes with respect to the normal as said earlier is denoted by . Angle starts from the negative angle w.r.t. normal and then increases for some time and then come back to the original position which can be seen in the walking cycle figure. Below figure shows the angle of the left and right thigh which it makes w.r.t. the torso. When either of the thigh angles goes to zero it means the thigh is straightened w.r.t the torso and is done when the leg strikes the ground which is shown in the walking cycle . So below graph shows the right and left thigh angle L and R. When the leg is raised from the ground, the knee is bended then again coming in line with the thigh just before again coming in contact with the ground. The figure shown below shows the knee angles L and R. Below shows the sensor values of the left and the right leg. When the leg is contact with the ground the value of the sensor is one and zero if it is not in contact with the ground. If one of the legs is taken the leg tip position in the x direction moves linearly and then zero for time until the other leg finishes the step and same is with the vertical movement the leg tip goes up and then comes back to ground and then remain zero until other leg comes back to ground. BIPEDAL RUNNING 8.1 Introduction (J.R.Ridgley, 2001) walking has been a focal point for a very large body of researchers, as it is considered the most basic form of legged locomotion with running as an enhancement. There is a popular phrase one must learn to walk before one can run. Less power and stress on the component of a system is required for walking. There is a significant practical advantage of the legged machines which can run over those limited to walking motion, but not much of a research has been done into the design of practical running machines. This is because there are a number of significant problems while constructing practical running machines. There are concerns which have been adequately resolved by modern technology. For example, mechanical structures and mechanisms can simply be developed which will consistently maintain the heaps of running, at least for devices developed on a reasonable extent of size for devices with masses on the order of 0.01kg to 100kg. At smaller extent than this, conve ntional machining methods are hard to use, and on larger scales the power requirements located on mechanical components may become unfeasible. Embedded control computers are extensively accessible which can easily process data rapidly enough to control the sensors and actuators which are expected to be used to control a running machine. Sensors which can calculate forces, accelerations, distances, angles, and velocities are easily accessible and only modestly expensive in contrast to other components of a typical robot. Actuators with adequate power density, for example electromagnetic and pneumatic actuators, are common. 8.2 Running Cycle Stance phase takeoff flight phase impact phase phase Figure. Running cycle (M.R.Anglin, 2011) running cycle can be described in two main categories flight phase and the stance phase. Each of thesephasesdefines the position of the foot at a certain portion of therunningcycle. Researchers who study a persons walking andrunninglocomotion can use the information obtained to find and solverunningproblems. The swing phase of arunningcycle occurs when none of the foot is in contact with the ground. The stance phase occurs between the time the leg tip is in contact with the ground and continues until the leg tip leaves the ground. The stance phase of arunningcycle can additionally be categorised into three sub phases: contact, mid-stance, and propulsion. During the contact sub phase, the leg tip comes in contact with the ground, and the sub phase carries on until the complete foot comes in contact with the ground. This contact can put a lot of pressure, occasionally equivalent to three times a persons body weight or more, onto the foot. After the contact sub phase comes the mid-stance sub phase. During this phase, the body bends forward and shifts over the foot to get ready for the next sub phase, the propulsion sub phase. A runner in the propulsion sub phase of therunninggait will see himself propelled forward. Straight away following this sub phase is the float phase. During the propulsion sub phase, the leg tip will leave the ground and the person is shifted forward. The sub phase ends with the leg tip taking-off the ground. Therunningcycle will continue until the foot touches the ground again, completing the cycle. 8.3 Robot Running Hypothesis (Westervelt et al, 2007) in order to ensure that the robots consequent motion satisfies the below properties consistent with the notion of a simple running gait, conditions on the controller will be imposed. Running can be categorised into three main phases single support, flight and impact. Throughout the contact, the stance leg end acts as an ideal pivot, during the single support phase. The ratio of the horizontal component to the vertical component does not excel the coefficient of static friction. The vertical component of the ground reaction device is non-negative. During the flight phase, a non-zero horizontal distance is covered by the centre of the mass. When the former swing leg end come in contact with the ground the flight phase ends. There is no slipping or rebounding of leg at impact. There is a symmetric motion of successive single support and flight phase with respect to two legs in the steady state. Running would take place on level surface from left to right. 8.4 Trajectory with telescopic legs (Raibert et al, 1986) and (T.DMcGeer, 1990) have deeply studied the running in the robots. (Gieger etal., 2001) are also working on the realization of a biped running robot. They have projected a running controller based on feedback linearization. (Shuuji Kajita, 2002) established a technique for running pattern generation using the dynamics of a simple inverted pendulum. In order to conduct the simulation a very simple has been taken with a point mass of m and a mass less telescopic leg. g l l y y Fz 0 Fz = 0 (a) (b) Figure. (a) the telescopic leg when in contact with the ground (b) takeoff phase The length of the leg in controlled as l=l0+sint l0 = neutral leg length = the amplitude of the vibration = frequency Fy is the reaction force and is zero when the foot is in the air but when in contact with the ground is given by Fy=ml+g=m(-2sint+g) g = gravitational acceleration In a certain phase Fy is negative when 2 g. This happens when the foot of the leg is firmly in contact with the ground. When Fy approaches zero it means that the foot is leaving the contact with the ground which means robot jumps into the air and then the robot takes a free fall trajectory. The liftoff timing A and the moment of takeoff yA can be written as A=1sin-1g2 yA=cosA=()2-(g)2 Now two legs are considered in the running model which is shown in the figure below. m lR lL y 0 Figure. Biped Model The length of the right leg lR can be represented as lR=l0+sint The time when both the foot are of the ground or the flight phase time Tflight can be written as Tflight=2yAg In order to achieve smooth landing the left leg lL length can be written as lL=l0+sint-delay Where delay can be formulated as delay=Tflight-22-A The velocity and acceleration of the mass change is continuous at the moment of landing. At the support phase the biped is supported by one of the legs so the duration of the support phase can be written as Tsupport=+2A Now the formulation for the horizontal locomotion is done in the sagittal plane (x,y) and for ideal condition it is assumed that the torque around the contact point equal to zero (y = 0). This results the constraint between floor reaction forces and mass location as FxFy=xy Fx = horizontal floor reaction force x = horizontal position The horizontal can be calculated as x=1mFx = -2sint+gl0+sintx The above equation is for the support phase where -At 2+A 8.5 Running with segmented legs The above model only had one degree of freedom in order to design a humanoid robot a two segment leg robot model would be discussed in detail. (J. Rummel, 2008) for this action a stance leg would be taken which is represented by a linear spring of rest length l0 and leg stiffness k. For this model only forces directed from a fixed contact point at the ground to the centre of the mass would be generated and the amount the amount of the force depends on the leg compressionl=l0-l(t). A constant leg stiffness k is assumed for a linear relationship between leg compression and leg force. Two mass less segments of length l1 and l2 defines the segmented leg. These two segments are connected by inter segmental leg joint with an inner angle . In order to produce spring-like forces in a segmented leg a torsional spring of stiffness c at inter segmental joint with joint torque, is introduced. =c =0- =denotes the amount flexion in the joint 0 = rest angle denotes the instantaneous joint angle and is defined as the function of leg length l and it can be written as l=cos-1(l12+l22-l2)2l1l2 Rest angle 0 which corresponds to a rest length of the leg is needed in order to calculate the amount of joint flexion l00=l12+l22-2l1l1cos(0) In consequence, any amount of joint flexion interprets into an equivalent amount of leg compression l depending on the selected rest angle 0. The leg force could be written as Fleg=ll1l2sin 8.5.1 Reference and effective stiffness Implementation A complete model of running on segmented legs would be modelled using simulink. The complete model is shown below Figure. Simulink model for running with segmented legs Firstly flight phase block would be described. In the flight control block the position of the leg x and y which are calculated before are subtracted from the position of the leg at touchdown which are written as yL=l0sin(0) xL=l0cos(0) When x xL is zero that means the leg is contact with the ground with the angle 0 and then the contact phase is triggered and then and the position are send to the next block for the calculation of contact force, the angle between the segments and the acceleration. The formulae of these parameters are already shown. The l during the flight changes according to simple Pythagoras theorem can be formulated as l=x2+y2 When the l0 = l that means it is contact with the ground and then the F, and a are calculated In the integration sub block the acceleration calculated is integrated to first velocity vx and vy and then again integrated to position x and y As yapex is the maximum height he leg goes and when the leg does not reach that height that means the leg has fallen and simulation is stopped and when the vertical velocity becomes zero that means one step is completed and then the step count is incremented. METHODOLOGY OF BIPEDAL RUNNING FUTURE WORK CONCLUSION