Design and Characteristics of Mode-Coupling LiNbO₃ Ultrasonic Motor Depended on Width-to-Length Ratio of the Stator Vibrator

Abstract

A miniature ultrasonic motor fabricated from a LiNbO 3 rectangular plate was studied to improve its rotation characteristics. In this motor, the coupling modes of in-plane longitudinal and flexural modes caused by crystal anisotropy are used to realize a single-phase drive motor. The mode coupling vibrator is designed to have crystal cut angles and the width-to-length ratio W =L of the vibrator shape. In this study, we noted the new coupling condition of W =L % 0:84 compared with the conventional ratio of W =L ¼ 0:255. We considered the mechanism of the mode coupling and the design of the stator vibrator by finite element method analysis and experiments. From the results, we fabricated and investigated prototype motors of the vibrator with dimensions of 10 Â 2:55 Â 0:5 and 4:10 Â 3:48 Â 0:5 mm 3 . The newly designed motor with the vibrator of W =L ¼ 0:849 improved the motor characteristics for the equalization of rotation in both directions. #

Review on single-phase driven ultrasonic motors

“…Bi-directional ultrasonic motors using mode coupling between the longitudinal and bending modes caused by the asymmetry shape (Aoyagi and Tomikawa, 1993; Aoyagi et al, 1992; Tamura et al, 2007) or crystal anisotropy (Tamura et al, 2008, 2010) of the stator were reported; the coupling effect could provide a pair of modes by asymmetry shape or crystal anisotropy; coupling mode is allotted to push the load in each direction; however, the output performances are not equal in each moving direction. Utilizing two same bending modes of a circle stator (Aoyagi et al, 2002; Takano et al, 1992, 1994, 1999), the same output performances in reverse direction were obtained; however, this type of structures was not suitable for effectively moving a linear slider directly.…”

“…The theory of two in-plane modes of a ring excited by a single-phase drive was discussed (Cagatay et al, 2003; Koc et al, 2000, 2002; Peter, 1987; Sashida, 1982; Ueha et al, 1993). Tubular ultrasonic motors utilizing only one drive signal were developed (Aoyagi et al, 2002; Cagatay et al, 2003; Chen et al, 2015; Friend et al, 2003; Ishii et al, 1993; Koc et al, 2000, 2002; Ma et al, 2016; Takano et al, 1992, 1994, 1999; Tamura et al, 2010; Ueha et al, 1993); This motor has two orthogonal degenerative bending modes, and only one excitation signal was supplied to one PZT element at a frequency between the resonance frequencies of the two modes, activating both modes and providing oscillating movement. The rotation direction could be reversed by changing the voltage to the other PZT element.…”

Single-Phase Drive Ultrasonic Linear Motor Using a Linked Twin Square Plate Vibrator

“…Typical studies of the single-phase driving-type USM were proposed using the L 1 mode of a piezo-laminated rectangular plate for application to watches and a microfan, 14,15) and provided thin miniature constructions and good characteristics; however, this type of USM cannot be rotated in the reverse direction. The single-phase-driven bidirectional USMs were reported using mode coupling between the L 1 and F 2 modes caused by the asymmetry shape [16][17][18][19] or crystal anisotropy 20,21) of the resonators. The coupling effect provides a pair of coupling modes.…”

Improvements in Controllability of Ultrasonic Linear Motors by Longitudinal-Bending Multilayered Transducers with Independent Electrodes

“…Ultrasonic motors have several advanced characteristics such as small size, a large holding torque without energy consumption, high resolution, and silence, because the driving force is caused by the piezoelectric vibration of a stator instead of electromagnetic interactions. [1][2][3][4][5] However, nonlinearity in the voltage-speed characteristics causes problems for precise control. Various control methods have been proposed to eliminate the nonlinearity.…”