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Journal of Zhejiang University SCIENCE A
ISSN 1673-565X(Print), 1862-1775(Online), Monthly
2016 Vol.17 No.9 P.724-732
Design of an ultrasonic motor with multi-vibrators
Abstract: This paper presents and verifies a new idea for constructing an ultrasonic motor (USM). The stator contains several vibrators fabricated by bonding piezoelectric ceramics (PZTs) to a metal base. When two alternating current (AC) voltages with a 90° phase difference are applied to the PZTs, longitudinal and bending modes are excited in the vibrator. The bending vibrations of the vibrators are stacked to form the torsional vibration of the stator, ultimately generating longitudinal-torsional composite vibration. Both vibrators and the stator are excited to the resonance state. A standing wave is formed by superposition of longitudinal and torsional modes. The proposed motor is an in-plane vibration motor because the vibrations of the stator are in the circumferential plane. The finite element method (FEM) is used to validate the feasibility of the proposed motor. The fabricated stator contains five vibrators. The tested resonance frequencies of longitudinal and torsional modes are 44.42 kHz and 43.83 kHz, respectively. The stall torque is 0.3 N·m and no-load speed is 45 r/min. The highest efficiency is 30%. The applied driving voltage is 100 Vo-p (peak voltage) at 43.9 kHz. The designed motor is a parallel-actuated integral motor. It allows the vibrators to operate synchronously, and overcomes asynchronous issues that occur in traditional multi-vibrator motors.
Key words: Ultrasonic motor (USM), Standing wave, In-plane vibration, Multi-vibrator
创新点：1. 提出圆周面内驱动的概念，发展已有的面内驱动概念（x-y面）；2. 提出一种模态转换方法, 通过多个振子弯曲振动的叠加形成设计电机的扭转振动；3. 电机工作时，不仅各个振子处于共振状态，而且连接而成的定子同样处于共振状态，有 利于提高电机的效率；4. 验证多振子同步驱动的机理。
方法：1. 振子采用贴片式结构，由极化方向沿厚度方向的压电陶瓷和金属基体粘结而成；与使用兰杰文振子相比，使用贴片式振子易于简化电机的结构。2. 各个振子首尾相连形成电机的定子，既可用于构造直线电机，又可转换成旋转电机。3. 通过有限元方法对不同振子数构成的电机定子进行性能比较，并且分析设计电机的驱动机理；此外，通过仿真分析确定电机的最优尺寸。4. 根据设计结果，加工原理样机，并且对加工的样机进行实验研究，探讨设计方法的可行性。
结论：1. 根据仿真分析结果，最终加工的电机定子包含5个振子。2. 定子中各个振子的振动特性完全相同，振子同步工作。3. 样机定子的内径为28 mm，外径为35 mm，高为30 mm；测得定子的纵振和扭转频率分别为44.42 kHz和43.83 kHz；当激励电压的频率为43.9 kHz、峰值为100 V时，电机的空载转速为45 r/min，堵转力矩为0.3 N·m，最大效率约为30%。4. 本文所设计的电机，是一种多振子并行驱动的整体式电机，具有结构紧凑和多振子同步工作等优点，能够克服常规的多振子电机在协同工作时出现的不同步问题；该设计方法可以为多振子电机的设计提供理论基础，推动超声电机在并行驱动方面的应用。
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DOI:
10.1631/jzus.A1500316
CLC number:
TM356
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On-line Access:
2016-09-08
Received:
2015-11-25
Revision Accepted:
2016-05-27
Crosschecked:
2016-08-23