３層構造を有するポリマー振動子を用いた超音波モータの特性評価に関するWu（PD）の論文が Sensors and Actuators A: Physical に掲載されました。
J. Wu, Y. Mizuno, and K. Nakamura, “Ultrasonic motors with poly phenylene sulfide/alumina/PZT triple-layered vibrators,” Sens. Actuat. A: Phys., vol. 284, pp. 158-167 (2018).
Our previously reported ultrasonic motors with poly phenylene sulfide (PPS)/lead zirconate titanate (PZT) double-layered vibrators were capable of providing high rotation speeds and light weight, but their output torques and power were limited owing to the low stiffness of PPS vibrating bodies. In this study, we constructed a triple-layered vibrator by sandwiching a thin alumina disk between the PPS vibrating body and PZT disk to compensate the stiffness. First, their fundamental vibration characteristics were investigated as some of key dimensions were varied. The force factor of the PPS/alumina/PZT triple-layered vibrator reached the maximal value when the neutral axis located at the boundary between the PZT and alumina disks. In contrast, the neutral axes existed in the PZT disks in the cases of PPS/PZT double-layered vibrators; this caused the relatively low force factors compared to the triple-layered vibrators. Subsequently, the load characteristics of the PPS/alumina/PZT triple-layered motors were experimentally assessed. The maximum output torque and power of the triple-layered motors were 5 and 13 times the values of the double-layered motors, respectively, owing to the enhanced force factors and electromechanical coupling factors. Besides, the optimal thickness was lower for the triple- than for the double-layered motor. These advantages indicate the potential of our newly designed triple-layered motors for practical applications.