Vibration Suppression of Robot Arm by Feedforward Control with On-Line Parameter Identification

Abstract

Generally, robot arms with flexible joints are multi-mass resonant systems, thus causing mechanical vibration. Since the vibration deteriorates the arm position control accuracy, the vibration suppression is indispensable to achieve the high performance arm motion. The authors have already proposed a feedforward vibration suppression scheme using an optimal control command shaping. The scheme is suitable for practical industrial use because of its simple control algorithm, however, there still remains a problem inherent in feedforward techniques that parameter setting errors in controller have significant effects on the suppression control accuracy.This paper presents an adaptive feedforward control of the vibration suppression with on-line mechanical parameter identifier, based on the proposed command shaping. In this scheme, the on-line identification of arm inertia using a method of least squares is performed during acceleration in arm motion. The identified parameter is used during deceleration to suppress the residual vibration. Experimental results using a prototype show the effectiveness of the proposed control.