Nano Positioning of a High Power Ultrasonic Linear Motor

In this paper, we present an investigation of the noble linear stage for high power and high precision positioning. The stage is driven by a hybrid-bolt clamped Langevin-type ultrasonic linear motor, which is vibrated at its different modes of resonance frequencies in both the lateral and longitudinal directions. To obtain a high power and high-accuracy motion, the driving frequencies of the two vibration modes must be simultaneous. In this study, to obtain well-matched vibration frequencies, the contact stiffness in the tangential and the normal directions are carefully considered in designing the actuator. In addition, deviations of the electro-mechanical characteristics of the lead zirconate titanate (PZT) actuator are considered in the bolt clamping process of PZT, and the exciting frequencies are adjusted through modification of the actuator length. Finally, the stage is controlled via proportional-integral-derivative (PID) control. As a result, positioning with a resolution of 20 nm and a moving speed of 78 mm/s was achieved with a linear sensor resolution of 15 nm.