Comparative Study of Pole Placement and Linear Quadratic Controller for Above Knee Prosthetic Leg

Lower limb prostheses are the basic requirement of amputees who have lost their limbs due to the war, accidents, natural disasters and any other physiological or motor system disorder. People with lower-limb amputations have remained the major concern among them. In this regard, researchers have designed different prosthetic limbs with various control strategies. Prosthetics can be grouped in two types on the basis of their working as active and passive. The focus of this research was to make active lower limb prostheses that imitate the motion of the real limb. This research is held for finding the mathematical model and simulation of above-knee prosthetic (AKP) for lower limb amputees. The transfer function and state-space model for 3 DOF AKP has been simulated using Simulink in MATLAB®. Controllability and observability of the model have been computed. Further, pole placement (non-optimal) and linear-quadratic (LQ) controller has been designed and compared for the system to control the motion of the AKP leg. The results show that optimal and robust controllers provide desired stability and control of the prosthetic by providing minimum energy.