TRACKING METHOD FOR THE CONTROL OF THE ABOVE-KNEE PROSTHESIS

The hierarchical control of an externally powered above-knee prosthesis is described in this paper. A rule-based expert system is used at the higher, strategic, level of control. This non-analytical, skill-based expert system is of on-off type and it does not take into account explicitly the dynamics of the man-machine system. To resolve problems introduced by an on-off control method, we decided to use a tracking control at the lower, actuator control level. This paper concentrates exclusively 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 mechanical properties of the system in the state space. The application of the tracking method is shown using the Belgrade active Above-Knee Prosthesis. The Belgrade artificial leg is a fully externally powered device with a single degree of freedom.