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A fuzzy controller is employed to control an electrohydraulic four-bar above-knee prosthesis for the swing phase in level walking. A two-dimensional (sagittal plane)mechanical model of the above-knee amputee is developed and the amputee prosthesis system is simulated for the swing phase. The man-machine system has two fuzzy controllers : a knee fuzzy controller which adjusts the knee damping moment so the prosthetic knee angle trajectory will track that of the patient's sound knee in the previous swing and a hip fuzzy controller utilized to model the way that an amputee will manipulate the prosthesis. From an optimal design procedure, a set of fuzzy controllers is found and an optimal relationship between variations of initial stump velocity and initial artificial shank velocity for the amputee is found. The results showed that the amputee swing gait can be controlled to a near normal one and walking with varied speed is possible.
Ju et al. (1995) studied this question.