Abstract: The shortage of the design test of the working modal frequency of the stator of ultrasonic motors is analyzed. Nonlinear property of the stator of ultra-sonic motors (USMs) and its frequency response property is analyzed. Hidden information of nonlinear property of the stator of USMs in the vibration re-sponse signal when excited with linear frequency modulated signal is analyzed. Points out that it is excellent to introduce time-frequency analysis theory to analyze the characteristic frequency of the stator of USMs. In developed in-plane vibration test system for USMs, using the time-frequency distribution spectrum got through time-frequency analysis of the vibration signal of the stator of USMs excited with linear frequency modulated sine wave, can quickly and conveniently uncover the information of the nonlinearity and characteristic frequency. The application example testifies that the means is efficient and feasible. And a scientific gist is provided to ascertain the fit working modal frequency of the stator of USMs.

Key words: Nonlinearity, Resonance frequency, Test, Time frequency analysis, Ultra-sonic motor