Mechanical design and friction modelling of a cable-driven upper-limb exoskeleton

This paper presents a lightweight and low-inertia cable-driven upper-limb exoskeleton powerful enough to meet the requirements for activities of daily living. It presents the mechanical design, kinematic structure,the underlying actuation system, sensors, other electronic components as well as the controller of the exoskeleton. The extensive effect of friction on cable-driven designs, such as the one presented in this paper, requires proper mathematical modelling for controller design. Thus, we propose a current actuator model that describes the relationship between the motor current, velocity, and external load. The model relies on an underlying Stribeck+Coulomb friction representation and an additional parameter that modifies its Coulomb friction representation with an offset to represent adhesion between a cable and sheath. The model has been validated based on experimental data collected with the exoskeleton. The results show that the proposed model better captures the non-linear behaviour of the exoskeleton’s actuation system, increasing overall descriptive performance by 15%. However, adding the adhesion offset to extend the relation of static friction, does not improve the model

Effect Of Food Supplementation On The White Blood Cells Count And Differential Leucocytes Count Of Trypanosome-Infected Pregnant Rats

Trypanosomiasis is an important livestock disease in sub-Saharan Africa. Improvement on host\'s nutrition is mportant in moderating the severity of pathophysiological efect of trypanosomiasis and it also influences the rate of recovery. Earlier researchers demonstrated that dietary supplement of selenium and vitamin E enhanced immune response in white rats. It has also been reported that during pregnancy, immune response is depressed. Leucocytes count has been recognized as a measure of immune response. This research was therefore conducted using chicks\' marsh fortified with 80 mg of vitamin E and 0.3 mg of selenum as control (Diet 1) to determine theefect of dietary suppementaton ofmoderate protein (combinaton of 250 g of corn meal, 240 g soyabean meal and 10 g of crayfish) inthe chicks\' mash (Diet 2), high dietary protein (combination of 400 g of caseinogen and 300 g o soyabean meal) (Diet 3), and high detary carbohydrate (combinaton of 400 g dextrose and 300 g cornmeal) (Diet 4) in the chicks\' mash on the white blood cells count and differential leucocytes count of trypanosome-infected pregnant rats. Dies 1 – 4 were given to rats in Cage A – D, respectively. The rats were nfected withtrypanosomes within 10th to 14th day of pregnancy. Each experimental set up was replicated three times. On comparing the total white blood cell counts of all the rats fed differen diets, there was no significant difference (P > 0.05) between the rats in Cage A (fed Det 1) and rats in Cage B (fed Diet 2), and similarly between rats in Cage C (ed Diet 3) and rats in Cage D (fed Diet 4). There was,however, significant difference (P < 0.05) between rats in Cage A and rats in Cages C and D, and also between rats in Cage B and those in Cages C and D Det 2 with a moderate (20.01%) proein leveland a balance of other nutrients produced the highest leucocytes count. Diet 2 therefore produced the highest immune response in the pregnant trypanosome-infected rats. Keywords: Trypanosomiasis, Nutrition, Leucocytes count, Immune responseAnimal Research International Vol. 4 (2) 2007 pp. 643-64

Advanced Animal Track-&-Trace Supply-Chain Conceptual Framework: An Internet of Things Approach

Information and data transmission, as well as total visibility in terms of supply chain track-&-trace, is seriously lacking in current industrial logistics-&-supply-chain management activities. This paper proposes the application of RFIDs and the Internet of things’ enterprise systems architecture to, propose a low-cost feasible cloud solution. This solution would keep track of health history, birth records, ownership history and track location of each animal by using an electronic solar-powered tag instead of the current passive ear tags. This paper employs GPRS, GSM and the Google Earth function along with RFIDs to design an enhanced proposed enterprise system-architecture framework in the form of a business process model. Various areas such as e-health, e-commerce, and cloud-based manufacturing have been revolutionized by discoveries in digitized practices. Advancements in the Internet of things led to the advent of asset tracking systems, condition monitoring and various intelligent systems that exchange data over the cloud. Farmers are very vulnerable to stock theft, straying animals and high business risks due to poor animal health management practices. Existing tracking systems have high ownership costs since some of them rely on GSM network providers whose services are costly for farmers. Innovations in digitized systems continue to add more value to businesses and individuals across broad range sectors. Authors of this paper propose a low-cost intelligent animal tracking system for an African free-ranging environment. Economies worldwide are ever becoming digital and animal husbandry practices stand to benefit from this digitisation approach

Wear mechanism of olivine at the small-scale: An in situ TEM study

The study of tribology includes wear, friction, and lubrication of interacting surfaces in relative motions. Since the function, efficiency, and lifetime of many engineering components depend on the appropriate friction and wear properties, the study of tribology has significant practical importance. However, traditional tribology tests are limited by the inability to observe real-time progress of the sliding contacts and wear mechanism. Recent developments in small-scale devices, particularly piezoelectric and MEMS-based actuators, aid in conducting scratches at the micro- and nano-scale in the TEM. Olivine is magnesium iron silicate (Mg²⁺, Fe²⁺)₂SiO₄ and the most abundant mineral in earth\u27s upper mantle, which comprises the bulk of the planet\u27s tectonic plates. Although the structure of olivine has been intensively studied by mineralogists and geophysicists, the frictional and mechanical properties particularly damage evolution at the small-scale of sliding contact is unknown. In this study, a bulk olivine sample was wedge polished and then fib-milled to prepare electron-transparent regions. A wedge diamond indenter of 100 nm radius and 3 um length was used to make sliding contact using a PI 95, TEM PicoIndenter. Multicycle scratch tests were conducted to understand wear behavior. During the wear passes, the kinetic friction coefficient remained relatively constant near 0.1 and substantial dislocation plasticity occurred in the sample. Each pass showed nucleation of additional dislocations which were arranged in a symmetric array along the wear path as shown in fig. 1. The talk will present a theory of friction and deformation behavior that are applicable to geological materials. Please click Additional Files below to see the full abstract

The impact damage response of plain woven natural silk/epoxy laminated composite plates

MoscowGrayscaleForman Nitrate Negatives, Box

Using humanoid robots to study human behavior

Our understanding of human behavior advances as our humanoid robotics work progresses-and vice versa. This team's work focuses on trajectory formation and planning, learning from demonstration, oculomotor control and interactive behaviors. They are programming robotic behavior based on how we humans “program” behavior in-or train-each other

Mechanical Properties of Heat-treated Medium Carbon Steel in Renewable and Biodegradable Oil

The heat treatment of steels under controlled conditions alters their physical and mechanical properties, enabling them to meet the desired engineering applications. In this study, the suitability of a Namibian local oil (marula oil) as an alternative quenchant to SAE40 engine oil (Standard quenchant – a synthetic oil derived from natural or crude oil) for industrial heat treatment of medium carbon steels was investigated. SAE40 engine oil served as the control. The mechanical properties (tensile strength, yield strength, percentage elongation and hardness) of the treated and untreated samples were investigated at the temperatures of 850oC, 900oC, 950oC and 1000oC. The untreated sample had the highest amount of elongation (40%), while the sample quenched in marula oil had the highest hardness (24.33HRD) and tensile strength (530.32 N/mm²) values compared with both the untreated and the SAE40 engine oil quenched samples. Hence, marula oil showed high potential as an alternative quenchant to petroleum based SAE40 engine oil for quenching medium carbon steels, without cracking or distortion

Analysis of genetic diversity in accessions of Irvingia gabonensis (Aubry-Lecomte ex O'Rorke) Baill

Amplified fragment length polymorphism (AFLP) was used to assess genetic diversity and relationships among 15 accessions of Irvingia gabonensis collected from Cameroun, Gabon, and Nigeria. Twelve AFLP+3 primers produced 384 polymorphic fragments. Average genetic distance (AGD) between the 15 accessions was 58.7% (32-88%). AGD and range of genetic distance among accessions from Cameroun, Nigeria and Gabon were 62% (53-76%), 52% (32.3 – 84.8%) and 50% (45- 53%), respectively, indicating more genetic diversity in Cameroun than Nigeria and Gabon. The unweighted pair-group method of the arithmetic average (UPGMA) and principal coordinate analysis (PCO) showed a clear distinction between the Gabon and Nigeria accessions into two separate clusters, with accessions from Cameroun overlapping them. Principal coordinate analysis (PCO) indicated a closer relationship between accessions from Cameroun and Gabon. In general the Cameroun germplasm appears to be a bridge between the genetically isolated Nigeria and Gabon accessions. This overlap of Gabon and Nigerian accessions by the accessions from Cameroun may be an indication that Cameroun is the center of diversity of I. gabonensis and also the primary source of original materials grown in the other countries. More collection in Cameroun is necessary to ensure the optimum collection and preservation of the existing genetic diversity in I. gabonensis.Keywords: Irvingia gabonensis, Accession, amplified fragment length polymorphism, genetic diversit