高次振動モードを用いたポリマー製超音波モータに関するWu（PD）の論文が IEEE/ASME Transactions on Mechatronics に掲載されました。
J. Wu, Y. Mizuno, and K. Nakamura, “Polymer-based ultrasonic motors utilizing high-order vibration modes,” IEEE/ASME Trans. Mechatron., vol. 23, no. 2, pp. 788-799 (2018).
Our previous study showed that traveling wave rotary ultrasonic motors with polymer-based vibrators provided limited output power when operating in the commonly implemented low-order bending vibrational modes. Thus, as a continuation, in this study, we employ a high-order bending mode in the polymer-based cylindrical ultrasonic motor, as this mode yields a relatively high electro-mechanical coupling factor, which may lead to increased output power of the motor. In contrast to the low-order modes with only vertical nodal lines, the high-order mode has both horizontal and vertical nodal lines on the circumferential outer surface of the polymer-based vibrator. Thus, it would be easier to firmly fix the vibrator via a horizontal nodal line. The effectiveness of the high-order mode in the polymer-based ultrasonic motor is experimentally examined. Polyphenylene sulfide, a functional polymer exhibiting low attenuation even under high-amplitude ultrasonic vibration, is used as the vibrating body that is activated by a piezoelectric ceramic element bonded onto the rear surface. The high-order mode can be generated on the polymer-based vibrator with a practically feasible thickness, although this mode is intrinsic to thick metal-based vibrators. The maximum output power available via polymer-based motors can be improved by utilizing the high-order mode; this maximum power is higher than that of metal-based motors operating in the same vibrational mode.