Control of stair ascent and descent with a powered transfemoral prosthesis.

This paper presents a finite state-based control system for a powered transfemoral prosthesis that provides stair ascent and descent capability. The control system was implemented on a powered prosthesis and evaluated by a unilateral, transfemoral amputee subject. The ability of the powered prosthesis to provide stair ascent and descent capability was assessed by comparing the gait kinematics, as recorded by a motion capture system, with the kinematics provided by a passive prosthesis, in addition to those recorded from a set of healthy subjects. The results indicate that the powered prosthesis provides gait kinematics that are considerably more representative of healthy gait, relative to the passive prosthesis, for both stair ascent and descent.

Standing stability enhancement with an intelligent powered transfemoral prosthesis.

The authors have developed a ground-adaptive standing controller for a powered knee and ankle prosthesis which is intended to enhance the standing stability of transfemoral amputees. The finite-state-based controller includes a ground-searching phase, a slope estimation phase, and a joint impedance modulation phase, which together enable the prosthesis to quickly conform to the ground and provide stabilizing assistance to the user. In order to assess the efficacy of the ground-adaptive standing controller, the control approach was implemented on a powered knee and ankle prosthesis, and experimental data were collected on an amputee subject for a variety of standing conditions. Results indicate that the controller can estimate the ground slope within ±1° over a range of ±15°, and that it can provide appropriate joint impedances for standing on slopes within this range.