Data-Driven Variable Impedance Control of a Powered Knee-Ankle Prosthesis for Adaptive Speed and Incline Walking | CU Experts

Most impedance-based walking controllers for powered knee-ankle; prostheses use a finite state machine with dozens of user-specific; parameters that require manual tuning by technical experts. These; parameters are only appropriate near the task (e.g. walking speed and; incline) at which they were tuned, necessitating many different; parameter sets for variable-task walking. In contrast, this paper; presents a data-driven, phase-based controller for variable-task walking; that uses continuously-variable impedance control during stance and; kinematic control during swing to enable biomimetic locomotion. After; generating a data-driven model of variable joint impedance with convex; optimization, we implement a novel task-invariant phase variable and; real-time estimates of speed and incline to enable autonomous task; adaptation. Experiments with above-knee amputee participants (N=2) show; that our data-driven controller 1) features highly-linear phase; estimates and accurate task estimates, 2) produces biomimetic kinematic; and kinetic trends as task varies, leading to low errors relative to; able-bodied references, and 3) produces biomimetic joint work and; cadence trends as task varies. We show that the presented controller; meets and often exceeds the performance of a benchmark finite state; machine controller for our two participants, without requiring manual; impedance tuning.

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