Testing an Electrohydrostatic Powered Ankle Prosthesis with Transtibial and Transfemoral Amputees

Powered lower-limb prostheses have the potential to assist amputees in the push-off phase during level walking, as well as stair and slope ascent. Compared to electromechanical actuation, the advantages of using eletrohydrostatic actuation (EHA) including high power density, low noise and good controllability. Especially for the application in lower limb prosthetic joints, an EHA provides a quick and smooth switch between passive and active operation modes. This paper presents the testing results using a new eletrohydrostatic powered ankle prosthesis which combines an EHA with a controllable passive damper. The new powered ankle prosthesis has been tested by both a transtibial and a transfemoral amputee. The test results show that the ankle prosthesis can provide sufficient power to assist toe push-off and subsequent foot lift (dorsiflexion) and operating passively in the rest of a gait cycle. The test results are compared with the ankle dorsiflexion angle and torque for healthy subjects. The timing control method and the performance of the EHA are discussed.