Hybrid vibration and rest-to-rest control of a two-link flexible robotic arm using H ∞ loop-shaping control design

Purpose – The purpose of this paper is to present a method for simultaneous motion and vibration control of light-weight slender robotic arms, known as flexible manipulators. In this paper, a new control algorithm is proposed for a two-link manipulator with elastic links. Design/methodology/approach – The controller includes a MIMO H ∞ Loop-Shaping Design (H ∞ LSD) as the feedback controller, and a command pre-shaping filter as the feed-forward controller. The conventional inputs and outputs of a typical two-link manipulator, that consists of the torques applied by the actuators at the joints, and the joint angles are chosen for the feedback control. Findings – It is shown that by selecting a proper desired loop shape, the H ∞ LSD is able to control the joint angles of the manipulator, and simultaneously, suppress vibrations of the system so that the high-frequency chatter due to the structural vibration modes does not appear at the outputs. Then it is shown that when the H ∞ LSD is equipped with a command pre-shaping filter, more efficient suppression of the chatter at the tip of the manipulator is achieved. The capability and effectiveness of the proposed control strategy in driving and stabilizing the manipulator to desired positions and simultaneously suppressing structural vibrations is shown by the simulation of the flexible manipulator in rest-to-rest maneuvers. Practical implications – The paper presents a flexible manipulator and looks at space manipulators. Originality/value – A robust MIMO controller is proposed for simultaneous motion and vibration control of flexible manipulator.