Impedance Control of a Knee Prosthesis with Frictional Torque Estimation

This paper presents the effects of adding friction torque estimation block on impedance control of manufactured knee prosthesis. The static and dynamic friction play an important role in the movements of manufactured knee prosthesis due to its components including power screw, timing belts, pulleys, etc. Fuzzy logic and LS identification method were used so as to estimate the demand friction torque in the movement of knee prosthesis. In order to design the fuzzy system, different motor velocities were utilized and the proper friction model was selected based on the Mean Absolute Square error (MSE) criterion. The results demonstrate proper knee angle tracking and also reducing the motor current demand in changing the movement direction of the knee prosthesis in swing phase.