Equivalent Circuit Modeling for V-Shape Linear Ultrasonic Motor

This work presented an improved equivalent circuit model (ECM) for a typical V-shape linear ultrasonic motor considering the real contact-based operating condition. A four terminal ECM is used to model the energy conversion of the stator under contact-based operating condition, where a nonlinear RC branch with an adjustable capacitance is included in mechanical branch for capturing the variable contact stiffness under different preloads. The friction drive mechanism is modeled by a thyristor rectifier with RL load to characterize the intermittent contact characteristics in standing-wave ultrasonic motors. The output terminal voltage of the rectifier is used as the input to a RL type ECM of the mover. Finally, the dynamics of the motor including the electrical admittance characteristics of the stator under contact-based boundary, the dead-zone behavior and the transient velocity response were validated and discussed by the proposed ECM.

1. Introduction

Compared with the traditional electrical machines, linear ultrasonic motor (LUM) is an attractive and advanced electro-mechanical actuator for various industry applications [1] due to its excellent merits such as high power and thrust density, friction self-locking and electromagnetic immunity. However, developing a generalized and practical theoretical analysis model for LUMs is still challenge due to their unique working principle based on the friction drive.