Precision positioning device using the combined piezo-VCM actuator with frictional constraint

This paper presents a new actuating method for a precision sliding stage using the combined piezo-VCM (voice-coil-motor) actuator. The proposed method is to employ the VCM to keep a presliding state of the sliding stage and then to use the piezoelectric (PZT) impact force to achieve precise motion. By controlling the forward or backward presliding state, the stage might undergo either directional motion due to PZT impact force, and thus have one degree-of-freedom of motion ability. Through fundamental experiments, the sliding stage was demonstrated to have various step motions on the order of as precise as 10 nm or as large as 10 μm. In addition, operational parameters which affected the motion characteristics of the stage, including applied voltage, pulse width, and normal load, were demonstrated. A dynamic model of the positioning device was established and verified as effective by numerical simulations. Finally, position control was performed to show that the positioning device has both large operational range and high-precision positioning ability. Using a traditional proportional-integral (PI) controller, the sliding stage was successfully positioned by the VCM with forward and backward target positions of 300 μm and 100 μm, and with the rough accuracy of 30 μm. The final precise accuracy of 10 nm was obtained by the PZT impact force for both forward and backward position controls. According to these experimental and numerical examinations, the remarkable positioning performance of the proposed device was well demonstrated.