A two-stage control scheme of single-link flexible manipulators

A new control scheme composed of two independent stages utilised to achieve precise positioning of single-link flexible manipulators is presented herein. Traditional techniques for the control of single-link flexible manipulators utilise only one actuator and two types of sensor measurement (e.g the angular position of the motor and acceleration or strain measurements) to move the manipulator and in order to damp the residual vibrations produced in the displacement of the manipulator. However, in the proposed control scheme another additionally pair actuator-sensor is utilised to improve the speed and precision of the controlled system. On the one hand a motor and the readings of a rotary encoder are utilised in a first stage to displace the manipulator, using the strain measurements in order to damp the high amplitude and low frequency residual vibrations. On the other hand piezoelectric actuators are utilised in conjunction with displacement measures of the tip of the manipulator in order to damp the low amplitude and high frequency residual vibrations which deteriorate the accuracy of the positioning achieved by the traditional control techniques. Simulation and experimental results are carried out to illustrate these improvements.