A rise time can be shorter by an electrical preload control with maintaining maximum revolution speed. The proposed equivalent circuit has possibility to easily simulate the performance of preload control.

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An ultrasonic motor using the L1-F1 mode with the rectangular plate is fabricated. Using a piezo-ceramic vibrator of 20 x 18 x 3 mm, the maximum speed of 130 mm/s at the input voltage of 90 Vrms, maximum force of 2.8N at the input voltage of 110 Vrms gaining the maximum efficiency of 1.8% are obtained. To improve efficiency, a newer electrode structure shall be advised and tested in the future. Characteristics of the efficiency in this fabricated motor is not so high. Therefore, it is necessary to consider another type of electrode configuration that enables the longitudinal movement and improve the efficiency. The ultrasonic motor of this type is characterized by a simple electrode structure and a relatively low driving frequency, and will find applications by making use of an easily realizable small size. Therefore, it is expected that the USM with a rectangular piezo-ceramic vibrator and the L1-F1 multiplex driving mode will have a promising future.

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In this study, we proposed a calorimetric method for measuring ultrasonic power that involves measuring the water temperature before and after ultrasonic irradiation. By using this method, problems associated with ultrasonic radiation including acoustic streaming, viscous heating and setting reproducibility can be removed. In the future, we intend to use this method to develop a standard for measuring the ultrasonic power.

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