Variable Structure Control Combined With Adaptive Iterative Learning Control for Motion Tracking of a Piezoelectric Microgripper

This paper proposes a novel controller to compensate for both the vibration and nonlinear hysteresis of a microgripper driven by piezoelectric actuators. The proposed control strategy includes two parts. The first part is an adaptive algorithm based on iterative learning control, and the second one is a feedback controller constructed by discrete-time sliding mode control. ILC has great properties to regulate repeating disturbance from previous steps, and it can also compensate for the error caused by hysteresis. In addition, the switching type of reaching law for the variable structure control of the discrete-time system is developed to realize the motion control of the piezo-driven gripper. The proposed control algorithm has been experimentally tested to verify its effectiveness on enhancing the performance in precision position control in comparison with conventional control schemes for the microgripper.