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Optimisation of bipedal walking motion with unbalanced masses. / Pooya Mahmoodi
Swansea University Author: Pooya, Mahmoodi
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Commercial prosthetic feet weigh about 25% of their equivalent physiological counterparts. The human body has a tendency to overcome the walking asymmetry resulting from the mass imbalance by exerting more energy. A two link passive walking kinematic model, with realistic masses for prosthetic, phys...
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Commercial prosthetic feet weigh about 25% of their equivalent physiological counterparts. The human body has a tendency to overcome the walking asymmetry resulting from the mass imbalance by exerting more energy. A two link passive walking kinematic model, with realistic masses for prosthetic, physiological legs and upper body, has been proposed to study the gait pattern with unbalanced leg masses. The 'heel to toe' rolling contact has significant influence on the dynamics of biped models. This contact is modelled using the roll-over shape defined in the local co-ordinate system aligned with the stance leg. The effect of rollover shape curvature and arc length has been studied on various gait descriptors such as average velocity, step period, inter leg angle (and hence step length), mechanical energy. The bifurcation diagrams have been plotted for point feet and different gain values. The insight gained by studying the bifurcation diagrams for different gain and length values is not only useful in understanding the stability of the biped walking process but also in the design of prosthetic feet. It is proposed that the stiffness and energy release mechanisms of prosthetic feet be designed to satisfy amputee's natural gait characteristics that are defined by an effective roll-over shape and corresponding ground reaction force combinations. Each point on the roll-over shape is mapped with a ground reaction force corresponding to its time step. The resulting discrete set of ground reaction force components are applied to the prosthetic foot sole and its stiffness profile is optimised to produce a desired deflection as given by the corresponding point on the roll-over shape. It is shown that the proposed methodology is able to provide valuable insights in the guidelines for selection of materials for a multi-material prosthetic foot.
College of Engineering