Nonlinear H∞ Controller Synthesis for Flexible Joint Robots

In this paper the design of an optimal nonlinear H∞ controller for flexible joint robot (FJR) is presented. An approximate solution based on Taylor Series expansion is considered for the Hamilton-Jacobi-Isaac (HJI) inequality. A two-degree-of-freedom controller combined of optimal nonlinear H∞ controller and inverse dynamics controller is proposed to tackle the regulation as well as tracking problem in FJR. The proposed optimal nonlinear H∞ controller attenuates the disturbance with a minimum achievable control effort, despite system parameter uncertainty. Simulation comparisons for single and multiple joint manipulators, show that the proposed controller yields to superior performance such as larger domain of attraction and smaller control effort as well as better tracking characteristics, compared to that of the others.