Automatic Stub Avoidance for a Powered Prosthetic Leg over Stairs and Obstacles

Passive prosthetic legs require undesirable compensations from their users to avoid stubbing obstacles and stairsteps. Powered prostheses can reduce those compensations by restoring normative joint biomechanics, but the absence of user proprioception and volitional control combined with the absence of environmental awareness by the prosthesis increases the risk of collisions. This video shows a novel stub avoidance controller that automatically adjusts prosthetic knee/ankle kinematics based on suprasensory measurements of environmental distance from a small, lightweight, low-power, low-cost ultrasonic sensor mounted above the prosthetic ankle. In a case study with two transfemoral amputee participants, this control method reduced the stub rate during stair ascent by % and demonstrated an 87.5% avoidance rate for crossing different obstacles on level ground. No thigh kinematic compensation was required to achieve these results. These findings demonstrate a practical perception solution for powered prostheses to avoid collisions with stairs and obstacles while restoring normative biomechanics during daily activities. This video is associated with the research article: S. Cheng, C. Laubscher, and R. Gregg, “Automatic Stub Avoidance for a Powered Prosthetic Leg on Stairs and Obstacles,” IEEE Trans. Biomedical Eng., Under review. This research was supported by the National Institutes of Health.