TRACKING METHOD FOR THE CONTROL OF THE ABOVE-KNEE PROSTHESIS

The hierarchical control of an externally powered above-knee prosthesi s is described in this paper. A rule-based expert system is used at th e higher, strategic, level of control. This non-analytical, skill-base d expert system is of on-off type and it does not take into account ex plicitly the dynamics of the man-machine system. To resolve problems i ntroduced by an on-off control method, we decided to use a tracking co ntrol at the lower, actuator control level. This paper concentrates ex clusively to the actuator control level and shows how the dynamics of the system was included into a finite state control. The strategic and actuator control levels are designed in the rather unconventional way in the output space, avoiding numerical complexity imposed by the mec hanical properties of the system in the state space. The application o f the tracking method is shown using the Belgrade active Above-Knee Pr osthesis. The Belgrade artificial leg is a fully externally powered de vice with a single degree of freedom.