A Millimeter-Scale Bar-Type Ultrasonic Motor Operating in Bending-Bending Vibration Modes

Small satellite constellations are becoming increasingly integrated with emerging services such as cloud computing and big data, which imposes strict requirements on compactness, light weight, low-power consumption, and high integration of space mechanisms. Herein, we report a millimeter-scale bar-type piezoelectric ultrasonic motor (USM) operating in the coupled resonant mode of two first-order bending (B1) vibration modes whose stator has an outer diameter of only 2 mm. Compared with conventional bar-type USMs driven by four excitation sources, the proposed configuration requires only two excitation signals, and the inner electrode does not need to be led out, thereby reducing both power consumption and fabrication difficulty. The dependence of output performance on driving frequency, driving voltage, and mechanical load was then systematically investigated. Specifically, at a voltage of 200 Vpp, the proposed motor achieved an output torque density of 0.85 μNm/mm3, which is more than 30% higher than those of typical reported USMs. Then, eight bar-type motors were integrated into one compact arrayed module as an application demonstration. These results indicate that the proposed miniature USM has excellent comprehensive actuation performance and great potential for precision driving in small satellite systems.