Comparative Between Backstepping and Adaptive Backstepping Control for Controlling Prosthetic Knee

Abstract

The lower limb amputees are increasing day by day. This has led to an increase in research in the field of prosthetic knee. In this work, a prosthetic knee was designed and developed to assist human movements and more quality of life for millions of individuals who have lost lower limbs. The dynamic model and parameter identification of a two degree of freedom (2-DOF) joint prosthetic knee is derived according to the Lagrangian dynamic approach. The two controllers Backstepping and Adaptive Backstepping are adopted to control the system. Stability analysis and controller design dependent on Lyapunov theory are assessed to prove a tracking of a desired trajectory. From the results, found that the quantitative comparison between the two controllers, showed significant improvement in results in position tracking. To comparison between Backstepping control and Adaptive Backstepping control, at the control action consumptions. It was found that the position error of the prosthetic knee in Backstepping control is by 9% at link 1 (thigh) and 7.4% at link 2 (shank) compared with desired trajectory, while in Adaptive Backstepping control is by 1.16% at link 1 and 1.65% at link 2 compared with desired trajectory. When comparing between Backstepping control and Adaptive Backstepping control, the improvement rate was 7.84 at link 1 and 5.75 at link 2 , the proposed Adaptive Backstepping control, it may be concluded, is more robust against this perturbation and to deal with uncertainty. Therefore, the controller is built in a MATLAB environment, and its performance and robustness are assessed. Index Terms— Prosthetic knee, Backstepping control, Adaptive Backstepping control, Lyapunov theory.