SPEED CONTROL OF ULTRASONIC MOTORS BY ADAPTIVE-CONTROL WITH A SIMPLIFIED MATHEMATICAL-MODEL

The ultrasonic motor is a new type of motor. In recent years, some mat hematical the ultrasonic motor have been reported. However, these mode ls are very complex to apply to control of the motor, and therefore sp eed or position controllers for this type of motor have been designed based on proportional and integral controllers or fuzzy controllers. S ince these controllers cannot take account of the motor's dynamics, a simple and convenient mathematical model of the ultrasonic motor is ne cessary in order to achieve high control performance. The authors prop ose a simplified mathematical model for the ultrasonic motor. which is expressed by a difference equation, and they then design a speed cont roller based on adaptive control theory. Adaptive control is attractiv e for controlling the ultrasonic motor because its speed characteristi cs vary with drive conditions. The effectiveness of the proposed contr ol scheme is demonstrated by experiments. Furthermore, the paper indic ates the influence of control delay and model orders on the mathematic al model experimentally.