Accurate measurement of speed, acceleration, blocking force and torque for actuators on the microscale is problematic by conventional means. Forces tend to be very low and time-scales relatively short. This paper describes experimental research on a non-contact technique that can be used to measure the performance of an ultrasonic piezoelectric micro-motor. A type of sensor-less speed measurement has been achieved by studying the frequency spectrum of the real power absorbed by two different motors. This shows a characteristic spike at low frequencies corresponding to the equilibrium rotational speed. The origin of this low frequency modulation is dependent on the impedance of the motors and the applied mechanical loads.
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