Controlled ultrasonic motor for servo-drive applications

Abstract

This paper deals with an advanced speed control scheme for inverter-fed travelling wave ultrasonic motors. It is implemented as an additional outer control loop of an underlaid voltage and travelling bending wave vector controller and verified by measurements on a prototype drive. The novel speed control is using an inverse contact model by a neural network, trained by measured values of speed and torque, in order to compensate the nonlinear torque generation of the motor. Since the reference values of the bending wave control are calculated from the desired torque value by the neu- ral network, first an open loop control of the drives torque is feasible and second common speed con- trol schemes, well performing in common electrical drives, can be applied. Thus, the so equipped ultrasonic motor-drive meets requirements for applications in the field of servo-drives e.g. robotics.