Towards local reflexive control of a powered transfemoral prosthesis for robust amputee push and trip recovery

Transfemoral amputees often suffer from falls and a fear of falling that leads to a decreased quality of life. Existing control strategies for powered knee-ankle prostheses demonstrate only limited ability to react to disturbances that induce falls such as trips, slips, and obstacles. In contrast, prior work on neuromuscular modeling of human locomotion suggests that control strategies based on local reflexes exhibit robustness to unobserved terrain such as slopes and steps. Therefore, we propose that a powered knee-ankle prosthesis governed by reflexive local controls will more competently adapt to unperceived disturbances. To test this hypothesis, we simulate a neuromuscular model of a transfemoral amputee walking over rough ground with a powered knee-ankle prosthesis governed by the proposed reflexive controller. We show that the proposed control allows the amputee to walk farther over rough ground than does the state-of-the-art control. The proposed controller also more readily rejects deviations from nominal walking gaits such as those encountered during a trip. These results suggest that applying the proposed control to a powered knee-ankle prosthesis will substantially improve amputee gait stability.