FUZZY CONTROL OF ELECTROHYDRAULIC ABOVE-KNEE PROSTHESES

A fuzzy controller is employed to control an electrohydraulic four-bar above-knee prosthesis for the swing phase in level walking. A two-dim ensional (sagittal plane) mechanical model of the above-knee amputee i s developed and the amputee prosthesis system is simulated for the swi ng phase. The man-machine system has two fuzzy controllers: a knee fuz zy controller which adjusts the knee damping moment so the prosthetic knee angle trajectory will track that of the patient's sound knee in t he previous swing and a hip fuzzy controller utilized to model the way that an amputee will manipulate the prosthesis. From an optimal desig n procedure, a set of fuzzy controllers is found and an optimal relati onship between variations of initial stump velocity and initial artifi cial shank velocity for the amputee is found. The results showed that the amputee swing gait can be controlled to a near normal one and walk ing with varied speed is possible.