Study on improving the resolution of an H-shaped piezoelectric ultrasonic actuator by stick-slip principle

Improving the performance of the motion stages driven by piezoelectric actuators is an enduring topic for expanding their applications. For the motion stage with a travel range of tens of millimeters, trade-offs are inevitable between getting high speed (hundreds of millimeters per second) and high resolution (tens of nanometers), due to the inherent limitations of the operating principles of the piezoelectric actuators. In order to improve the output resolution of an H-shaped piezoelectric ultrasonic actuator, sawtooth excitation voltages are used in this work rather than the conventional sinusoidal voltages in previous works. The configuration and operating principle of the actuator are discussed in detail. The actuator consists of two vertical and two horizontal longitudinal transducers. The ends of the vertical transducers act as the driving tips and drive the stage forward with the alternating slow extensions and rapid contraction, during which stick motions and slip motions of the stage are acquired. An analytic model is developed to estimate the horizontal and vertical output displacement of the driving tip. The maximum error between the predicted value of the analytical model and the experimental value is about 14%. A prototype of the motion stage is fabricated and experiments are carried out to evaluate its output characteristics. The experiment results confirm the operating principle and show that the resolution is upgraded to tens of nanometers. The prototype obtains a resolution of 19 nm, a maximum speed of 2.22 μm s⁻¹, and a maximum carrying load of 16.94 kg.