Control of a high precision stage using a walking piezo actuator

Piezoelectric actuators are commonly used for positioning high precision stages. The need for new actuators and drive principles are being invoked by the increasing demands regarding speed and accuracy. The used walking piezo actuator is a non-resonant piezoelectric actuator that can drive a stage through four piezoelectric drive legs. In this paper, the piezo actuator is used to drive a stage with one degree-of-freedom. A model of the stage and the piezo actuator was made to develop and test a feedback control strategy. A new drive principle was developed, which results in overlapping tip trajectories of the drive legs and a continuous and smooth motion of the stage. Feedforward control and gain scheduling further improve the performance. Constant motion up to 2 mm/s is performed with a tracking error below 400 nm. Point-to-point movements of 5 nm up to the complete stroke of the stage are performed with a final static error below the encoder resolution.