Stable Forward Dynamic Simulation of Bipedal Gait Using Space-Time AnalysisReport
Within the biomechanist community, there is a rhetorical hypothesis that both movement trajectory and joint torque are modulated or adapted to maintain dynamic stability in bipedal walking. Not only are these two control variables intricately related, but such additional objectives as desired speed, stealth, endurance, etc. inevitably contribute to the complex behavior in animal locomotion. As a consequence, any single objective function used to describe walking dynamics is necessarily limited. We propose a bipedal walking control algorithm that simultaneously solves for movement trajectory and joint torque without relying on any a priori assumptions regarding one or the other. The absence of such assumptions permits the study of pathologic movement dysfunctions where the desired movements and torques are unknown. Our technique uses a constraint-based space-time optimization algorithm to compute optimal movements and torques. Such pathologic constraints as leg-length discrepancy, range-of-motion limitations, or velocity constraints from spastic hypertonia may be added and this optimization technique will find non-homogeneous solutions. When this technique is applied to a control task with a known optimal solution, two-segment downhill walking, it produces identical results to a torque-free forward-integration approach. Solutions to pathologic behavior conditions were also demonstrated by limiting swing leg velocities to simulate the neuro-physiologic constraints of hamstring spasticity. 1
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Granata, Kevin, David Brogan, and Pradip Sheth. "Stable Forward Dynamic Simulation of Bipedal Gait Using Space-Time Analysis." University of Virginia Dept. of Computer Science Tech Report (2002).
University of Virginia, Department of Computer Science