Abstract
In this study, we design and fabricate a tank-track-shaped stator working in two torsional modes to form a traveling-wave (TW) linear ultrasonic motor (USM). The stator comprises two torsional transducers and two kidney-shaped vibrating bodies. When voltages with a certain phase are applied to the transducers, two in-phase TWs are excited on the vibrating bodies to frictionally drive the slider. Here, the torsional vibration guarantees strong electromechanical coupling, and meanwhile, the tank-track shape ensures plural driving points and low weight; these features may facilitate realizing high thrust force density and high power density of linear motors. To examine the feasibility, first, we constructed a stator prototype 116 mm in length, 91 mm in width, and 32 mm in thickness and explored its vibration properties. The minimal standing wave (SW) ratio reaches 1.21 and the small SW components are desirable for TW motors. Then, we measured the load characteristics and found that, at the working frequency of 54.34 kHz and the phase shift of -110°, the maximal thrust force and maximal output power were 96.1 N and 27.8 W, respectively. Moreover, the thrust force density and power density reached respectively 234.1 N/kg and 67.8 W/kg, relatively high compared to the values of most conventional linear motors. This study verifies the feasibility of our proposal and paves a new way of designing powerful linear USMs.
Highlights
Ultrasonic motors (USMs) convert electrical energy to mechanical energy on the basis of inverse piezoelectric effect and achieve actuation by frictional force [1]–[3]
It is known that vibration modes have fundamental effect on thrust force density and power density [16], [17]
B2 modes have been heavily exploited in conventional USMs
Summary
Ultrasonic motors (USMs) convert electrical energy to mechanical energy on the basis of inverse piezoelectric effect and achieve actuation by frictional force [1]–[3]. Two kidney-shaped vibrating bodies are connected onto bilateral surfaces of two parallelly-arranged torsional transducers to form a tanktrack-shaped stator. Since two TWs in phase exist on the vibrating bodies, whose lengths are smaller than one wavelength, it can be equivalently regarded that this motor has two driving feet [1], [14], [22]; this contributes to enhancing driving force. B. DESIGN PROCEDURE To obtain high thrust force density and high power density, we investigate how the keff /m ratio changes with varying dimension (where keff and m are respectively the effective electromechanical coupling factor and the stator’s weight). Fr s have a discrepancy of
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