Electric-mechanic-thermal coupling calculation model for transient performance of ultrasonic motor

Working continuously in a confined space, the temperature rise of the ultrasonic motor cannot be neglected, and the dynamic performance is sensitive to temperature effects. This research aims to propose a new theoretical model to effectively demonstrate the electric-mechanic-thermal coupling characteristics of the ultrasonic motor. The integration of thermal stress and time-varying parameters related to temperature into the model leads to the establishment of an electric-mechanic-thermal coupled dynamic model. The present model achieves simultaneous evaluation of the mechanical and temperature characteristics of ultrasonic motor. Further experiments validate that the transient characteristics changing of ultrasonic motor can be predicted by the proposed model. The experimental and calculated average errors of motor temperature rise and performance are 1.23% and 2.21%, respectively. This model demonstrates the variation of mechanical characteristics of ultrasonic motor under different temperature fields, and the performance can be controlled to remain basically unchanged by controlling the frequency to decrease by 10 Hz for every 1 °C decrease in temperature. This model can guide the design and control optimization of ultrasonic motor, and enhance the thermal management strategies for ultrasonic motor applications.