Study on Large Capacity Ultrasonic Motor Using Principle of Strain Wave Gearing

本研究以研制体积小、重量轻、功率大的电动执行器为目标，研制了两种不同于传统超声电机工作原理的超声电机，一种采用多层压电器件，另一种采用环形压电器件。在该电机中，行波是由应变波传动和弯曲波原理产生的，转子是由摩擦力机械驱动的。本研究的结果如下：(1)采用高刚度、大输出功率的环形压电装置，设计并试制了谐振式压电电机（超声波电机）。此外，对较早研制的多层压电电机进行了改进，提高了其机械刚度和性能，获得了阐明该电机存在问题的基础数据。(2)对矩形电流波形和滤波后矩形电压波形的FET逆变器电路进行了改进，以获得更好的波形和控制灵活性。(3)改进了电机转矩与转速的测量装置，考虑到改进电机可能提高转速。(4)对于采用环形压电装置的电机，进行了两种电机的试制和比较。一个是电机使用的设备不分割，另一个是使用的设备平均分为6个部分。结果表明，电机转矩与转速的特性不受装置划分的影响，而受电机定子的机械性能的影响。(5)阐明了环形压电装置与电端子接触条件对电机特性的影响。特别是对于分环式器件，接触层厚度对其特性影响较大，因此有必要使接触层尽可能薄。(6)研究发现，在使用环型器件的情况下，由于施加的电压越高，器件内部的功率损耗越大，器件温度会有较大的升高。有必要对电机定子的结构进行改造，利用装置的大应力，而不用装置的大位移，提高定子表面的切向速度。(7)对于采用多层式压电装置的电机，为了提高电机的机械刚度，有效地将装置的位移传递给电机定子，在试验中采用了一种与电机底座对称的新型结构。少

In this study, aiming at development of compact, light-weight large power electrical actuators, two types of ultrasonic motors, whose operational principle differed from that of the conventional ultrasonic motors, were developed, one using multi-layr type piezoelectric devices and the other using a ring type piezoelectric device. In the proposed motors, the traveling waves were generated by the principle of the strain wave gearing and the bending wave and the rotors were driven mechanically by the friction force.The results of this study are as follows ; (1) A resonant type piezoelectric motor (ultrasonic motor) was designed and made on a trial basis using a ring type piezoelectric device with high stiffness and large output power. Moreover, the multi-layr type piezoelectric motor developed earlier was also improved for higher mechanical stiffness and better characteristics, and basic data for clarifying the problems of the motor were obtained. (2) The main circuits and its control cir … More cuits of the FET inverters with rectangular current waveforms and filtered rectangular voltage waveforms were improved for better waveform and control flexibility. (3) The measurement equipment of the motor torque versus rotational speed was improved making allowance for possible increase of the rotational speed by improvement of the motor. (4) In regard to the motor using the ring type piezoelectric device, two types of motors were made on a trial basis and compared. One was a motor using the device not divided and the other was that using the device equally divided into 6 parts. As a result, the characteristics of the motor torque versus rotational speed were not so influenced by the division of the device but by the mechanical properties of the motor stator. (5) It was clarified that the characteristics of the motor was influenced by condition of contact between the ring type piezoelectric device and the electric terminals. Especially, in the case of the divided ring type device, the characteristics were considerably influenced by the thickness of the contact layrs and, therefore, it is necessary to make the contact layr as thin as possible. (6) It was found that the higher applied voltage resulted in the considerable increase of device temperature due to the power loss in the device in the case of using the ring type device. It is necessary to reform the structure of the motor stator so as to increase the tangential speed on the surface of the stator by using the large stress of the device without the large displacement of the device. (7) In regard to the motor using the multi-layr type piezoelectric device, a new type structure which was symmetrical with respect to the motor base was employed in a trial basis in order to increase the mechanical stiffness of the motor and transmit the displacement of the device to the motor stator effectively. Less