loading page

Automatic Stub Avoidance for a Powered Prosthetic Leg over Stairs and Obstacles
  • Shihao Cheng ,
  • Curt Laubscher ,
  • Robert Gregg
Shihao Cheng
University of Michigan

Corresponding Author:[email protected]

Author Profile
Curt Laubscher
Author Profile
Robert Gregg
Author Profile


Passive prosthetic legs require undesirable compensations from amputee 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 paper presents 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 89.95% 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.
2023Published in IEEE Transactions on Biomedical Engineering on pages 1-12. 10.1109/TBME.2023.3340628