A Traveling Wave Ultrasonic Motor Using Polymer-based Vibrator

Having natures of low speed, high torque and quick response characteristics, ultrasonic motors (USM) are applied in robot, precision machine and optical instruments. A lightweight actuator is essential to decrease the total weight and increase the operability. Although USMs, in general, are superior to conventional electromagnetic motor in torque/weight ratio, lighter motor is demanded. In this research, we mainly focus on using low density materials to decrease weight. In recent reports, by making USM with polymer-based bending vibrator and measuring its mechanical characteristics, we knew that, comparing with metal-based ones, USMs with polymer-based vibrator has higher rotary velocity and lower maximum torque [1], polyphenylenesulfide (PPS) can be considered as the most appropriate polymer among tested ones. However, the driving frequency of the bending vibrator was approximately 4.5 kHz. It should be confirmed whether mechanical loss is low enough and polymer-based USM can be driven within ultrasonic frequency range experimentally. In addition, as one important parts in USM, contacting surface and rotor also have influence on the motor’s performance, thus, material is worthy of being chosen carefully. Aiming at solving these problems, in this paper, we examined a PPS-based annular vibrator and several disk-shaped rotors made of different materials to form traveling wave USMs, and measured the vibration and mechanical characteristics to answer the questions mentioned above.