This report is the result of a master thesis work where the goal was to develop a control system for a type of ultrasonic motor. The ultrasonic motors useultrasonic vibrations from a piezoelectric material to produce a rotating motion.
They are powered by two sinusoidal voltages and their control signals generally are the voltages amplitude, frequency and the phase difference between the two voltages.
In this work the focus is on control using only amplitude and frequency. A feedback signal was provided by an encoder, giving an angular position. The behavior of the motors were investigated for various sets of control signals. From collected data a linearized static model was derived for the motor speed.
This derived model was used to create a two part control system, with an inner control loop to manage the speed of the motors using a PI controller and an outer control loop to manage the position of the motors. A simple algorithm was used for the position control and the result was a control system able to position the motors with a 0.1 degree accuracy. The motors show potential for greater accuracy with a position feedback, but the result in this work is limited by the encoder used in the experiments.
Source: Linköping University
Authors: Arkad, Jenny | Andersson, Tomas