Position control of a two-link flexible manipulator featuring piezoelectric actuators and sensors

This paper presents a hybrid actuator scheme to actively control the end-point position of a two-link flexible manipulator. A highly nonlinear system model including inertial effect is established using Lagrange's equation associated with assumed mode method. Control scheme consists of four actuators; two servo-motors at the hubs and two piezoceramics attached to the surfaces of the flexible links. Two sliding hyperplanes which have time-varying parameters are designed for two servo-motors. The surface gradients of the hyperplanes are determined by pole assignment technique to guarantee the stability on the hyperplanes themselves. The sliding mode controllers corresponding to the hyperplanes are then synthesized on the basis of an equivalent rigid-link dynamics to the proposed flexible manipulator. During the motion, undesirable oscillations caused by the torques based on the rigid-link dynamics are actively suppressed by applying feedback control voltages to the piezoceramic actuators. Consequently, the desired end-point motion is achieved. In order to demonstrate the effectiveness of the proposed methodology both regulating and tracking control responses are evaluated through experimental realization. (C) 2001 Published by Elsevier Science Ltd.