Improving the performance of medical robotic system using H∞ loop shaping robust controller

Abstract

To solve the relevant open problem of precise tracking, the current research synthesises a robust controller via H∞ loop shaping for a human swing lower limb system. The human walking is sophisticated with particularly nonlinear dynamics. It is interpreted as a pendulum links representing human thigh and shank. Reliable and efficient controller for a human swing leg robot system faces serious problems due to weight variations, modelling uncertainties and different disturbing effects. This work considers these constraints through designing a robust controller based on loop-shaping framework. It provides an appropriate approach to compromise robustness and tracking precision despite variation of weight factors, and model uncertainty. To obtain muscle gestures, two necessary control actions were developed and applied at the joints. Robust stability and tracking were demonstrated rigorously. The obtained results from numerical examples confirm the effectiveness of the proposed controller as well as its remarkable simplicity.