Position control of a two-link flexible manipulator using piezoelectric actuators

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 effects is established using Lagrange's equation associated with assumed mode method. Control scheme consists of four different actuators; two servo-motors at the hubs and two piezoceramics bonded 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 sliding mode conditions. 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, desired tip motion is achieved. In order to demonstrate the effectiveness of the proposed methodology experiments are performed for the regulating and tracking control problem.