2端子対超音波モータ等価回路のパラメータ同定の留意点

概要

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Almost all of the equivalent circuit for ultrasonic motor is expressed as a one port circuit. However, an equivalent circuit with two-port pair is furthermore convenient, because both the phase and the voltage difference controls can be simulated. According to the research on literature, a parameter identification method was previously proposed for the two-port pair circuit. Identifying of circuit parameters is impossible. Then, in this paper, the matters that require attention are summarized and a revised method is proposed. Firstly, the practical equations to evaluate the parameters are derived. Next, we point out that the parallel supply test is unfit for the parameter identification, because the motor cannot rotate. To overcome this issue, the modified parallel supply test is proposed. Finally, it is shown that all circuit parameters are easily derived under the limited condition, i.e. the stator only and the USM without preload. While the parameter identification for the USM with preload is a failure.