Abstract text

An ultrasonic actuator includes: an actuator body (5) including an actuator body (50); a control circuit (150) for setting a driving frequency; power supply sources (191, 192) for applying a driving voltage having the driving frequency to the actuator body; and a memory (170) for storing data related to a difference between antiresonance and resonance frequencies of the actuator body (50). The control circuit (150) determines, based on a reference frequency where a current value of a current fed to the piezoelectric element (50) is local minimum and the data stored in the memory (170), a lower limit of a control range of the driving frequency so that the lower limit is equal to or higher than a frequency where the current value of the current fed to the piezoelectric element (50) is local maximum and determines the driving frequency to be a frequency in the control range.