Generally, wheelchair users cannot move easily within buildings since living areas in architectural structures are not suitable for them to maintain or to improve their physical capabilities. Because living area restrictions affect the physical performance of the users outside during the day, the reduced mobility causes several health problems. These problems become more intense by the time. Especially heart and lung related illnesses are common among the wheelchair users since the immobility decreases respiration capacity. The aim of this research is to design and prototype a wheelchair treadmill to help wheelchair users improve their upper extremity system. In this study, CAD was employed for the design of wheelchair treadmill. Then finite element analysis (FEA) was carried out for the parts of the wheelchair treadmill and the prototype was manufactured based on the results. The prototype was tested under the conditions the product was originally intended to function. In the experiments, the speeds of wheelchair and wheelchair treadmill were measured. The distances taken by users were also recorded, and the results were evaluated with respect to road surface conditions.
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In this paper, an R-C-D turn-off snubber circuit for power MOSFETs has been designed. Since the MOSFET operates at high switching frequencies and there is no way to avoid stray inductances in the circuit due to the connection cables, it is necessary to limit dv/dt of the MOSFET at turn-off. First, PSPICE model of the switching circuit has been obtained and then the effects of the connection cables on the MOSFET voltage has been demonstrated. An appropriate snubber circuit across the MOSFET has been used. The circuit which energies an inductive load from a dc supply has been designed by considering the results from the PSPICE model. Both simulation and experimental results are presented to confirm the correct operation of the snubber circuit.
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