No abstract

This paper presents the operating principle of the ultrasonic motor (USM) as a new actuator and its steady-state characteristics for application-specific servo motion systems. The latest developed inverter-drive traveling wave type ultrasonic motor (TUSM) is suitable for direct-drive motion systems. We describe a positioning servo motion system using the TUSM, which operates under a feasible fuzzy-reasoning controller with velocity and positional state-variable feedback schemes. Experimental verifications are given and their results are evaluated using a one-axis servo motion drive system. It is also proved that a new compact direct-drive servo motion system using inverter-fed USM which incorporates a microprocessor-based two-input and one-output fuzzy-reasoning controller is more acceptable for a specific direct-drive application.

Thispaper describes the schematicreview o f Travelling-wave type Ultrasonic Motor (T-USM) and a newly-proposed weigt-quality speed tracking controller of T-USM on the basics o f the computer software-based varia ble-gain adjustm en t stra tegy.Its speed tracking characteristics capable o f improving speed ripple, speed regulation and speed tracking characteristics are feasibly demonstrated i n experiment as compared with a previously-developed fuzzy-logic speed controller of T-USM actuated servo drive system. I t is proved that T-USMspeed control scheme developed herein i s practically acceptable for direct-drivespeed servo system.

The driving force of ultrasonic motors (USMs) is the frictional force between the ultrasonic vibrating stator and the rotor. A mechanical resonance of the stator is utilized for expanding the amplitude of stator vibration. The mechanical resonant frequency of USMs is variable according to the temperature rise of USMs and the change of load applied to them. In order to drive and control USMs stably, the driving frequency of a high-frequency power source must track or match the resonant frequency of USMs. Therefore, detection of resonant state on USM is required. This paper describes a resonance detecting method of the USM with a piezoelectric element sensor mounted on the stator. The phase difference between the generated voltage by this sensor and the applied voltage to the USM indicates the resonant state of the USM, which is derived from the fundamental equations of electromechanical conversion theory and piezoelectric effect. This effective resonance detecting method is experimentally demonstrated using a computer-based measuring system.