Knee Bending Prevention System for Robotic Knee Prosthesis Using Finite State Machine

During walking with trans-femoral prostheses, lower limb amputees have risks of tripping due to knee bending, in which the knee joint unexpectedly flexes. Since the trips lead to serious injuries such as broken bones, knee bending affects daily life quality. In recent years, robotic technology has been used to develop trans-femoral prostheses that don’t cause the knee bending. In general, in order to avoid tripping, even when the foot contact the ground with the knee joint in flexion, it is important to return to normal walking after stepping on the prosthetic leg. However, since the conventional robotic prostheses doesn’t control the flexion angle of the knee joint that enables the prevention of tripping, they have risks of tripping when the amputees unexpectedly lost their balance. Therefore, in this study, we constructed trip-avoidance strategy based on a mathematical formulation of the flexion angle of the prosthetic knee joint according to the assumed knee bending pattern during walking and designed a new knee bending prevention system for robotic knee prostheses. Finally, we conducted experiments that simulate knee bending by a user of trans-femoral prosthesis and showed the effectiveness of proposed method.