State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, China.
PLoS One. 2010 Apr 2;5(4):e10020. doi: 10.1371/journal.pone.0010020.
Ultrasonic motors (USM) are based on the concept of driving the rotor by a mechanical vibration excited on the stator via piezoelectric effect. USM exhibit merits such as simple structure, quick response, quiet operation, self-locking when power off, nonelectromagnetic radiation and higher position accuracy.
A cylindrical type traveling wave ultrasonic motor using cantilever type composite transducer was proposed in this paper. There are two cantilevers on the outside surface of cylinder, four longitudinal PZT ceramics are set between the cantilevers, and four bending PZT ceramics are set on each outside surface of cantilevers. Two degenerate flexural vibration modes spatially and temporally orthogonal to each other in the cylinder are excited by the composite transducer. In this new design, a single transducer can excite a flexural traveling wave in the cylinder. Thus, elliptical motions are achieved on the teeth. The actuating mechanism of proposed motor was analyzed. The stator was designed with FEM. The two vibration modes of stator were degenerated. Transient analysis was developed to gain the vibration characteristic of stator, and results indicate the motion trajectories of nodes on the teeth are nearly ellipses.
The study results verify the feasibility of the proposed design. The wave excited in the cylinder isn't an ideal traveling wave, and the vibration amplitudes are inconsistent. The distortion of traveling wave is generated by the deformation of bending vibration mode of cylinder, which is caused by the coupling effect between the cylinder and transducer. Analysis results also prove that the objective motions of nodes on the teeth are three-dimensional vibrations. But, the vibration in axial direction is minute compared with the vibrations in circumferential and radial direction. The results of this paper can guide the development of this new type of motor.
超声波电机（USM）基于通过压电效应在定子上激励机械振动来驱动转子的概念。USM 具有结构简单、响应迅速、运行安静、断电自锁定、无电磁辐射和更高的位置精度等优点。
本文提出了一种基于圆柱型行波超声电机的悬臂式复合换能器。在圆柱体外表面上有两个悬臂梁，在悬臂梁之间设置了四个纵向 PZT 陶瓷，在每个悬臂梁的外表面上设置了四个弯曲 PZT 陶瓷。通过复合换能器激励圆柱体内的两个空间和时间相互正交的简并弯曲振动模式。在这种新设计中，单个换能器可以激发行波在圆柱体内的弯曲行波。因此，在齿上实现了椭圆运动。分析了所提出的电机的驱动机构。采用有限元法对定子进行了设计。定子的两个振动模式退化。进行了瞬态分析以获得定子的振动特性，结果表明齿上节点的运动轨迹几乎是椭圆的。
研究结果验证了所提出设计的可行性。圆柱体内激发出的波不是理想的行波，且振动幅度不一致。行波的变形是由圆柱弯曲振动模式的变形产生的，这是由圆柱和换能器之间的耦合效应引起的。分析结果还证明了齿上节点的目标运动是三维振动。但是，轴向振动与周向和径向振动相比非常微小。本文的研究结果可以指导这种新型电机的发展。
