Robust 2-DoF Controller Design using H∞ Synthesis for Flexible Robots

Abstract

Fast-response with high-precision positioning for industrial robots is an indispensable requirement in a wide range of applications. Nonetheless, resonant vibrations due to flexibilities in mechanical structures generally deteriorate their motion performance. A practical approach to achieve fast and precise positioning is to use a two-degree-of-freedom (2-DoF) control system with feedback and feedforward compensators. Conventionally, a cascade feedback control system is constructed based on P-PI control, where the position and velocity controllers are respectively implemented using a proportion (P) and a proportion-integrator (PI). The paper proposes robust vibration suppression using H∞ control as an alternative design for the feedback compensators in the 2-DoF cascade closed-loop control framework of a flexible robot arm. Acceleration feedback is also applied to improve the control performance. The effectiveness of the proposed design has been verified by conducting experiments using a prototype.