Optimal Backstepping Controller Design for Prosthetic Knee Joint

Abstract

The mobility of people who have had a lower limb amputated is slower, less stable, and needs more metabolic energy than the movement of physically fit, also, often have difficulty moving on uneven terrain and stairs. In most cases, these problems may be traced back to the usage of controllers for an above-knee prosthesis, which enhances movement and more quality of life for millions of individuals who have lost lower limbs. In this work addresses the dynamic modeling and parameter identification of the lower limb, and the control of a 2-DOF joint prosthetic, because the uncertainty, high nonlinearity, problems with imbalance, and external perturbations, which can occur during movement. Backstepping control algorithm based on the Lyapunov theory was used, this is to ensure system stability with enhanced dynamic performance. The Bat algorithms optimization technique was used to fine-tune these design parameters to improve the performance of the proposed controller. From the results, found that the quantitative comparison between the present study and the related articles previously published which used sliding mode observer control, showed reasonable agreement. To comparison between convolution Backstepping control and optimal Backstepping control with Bat algorithms, at the control action consumptions. It was found that the position error of the prosthetic knee is enhanced by 9% at joint1 and 7.4% at joint2, respectively. Therefore, the results are considered satisfactory for such biomedical systems.