Rotary actuator and method of controlling an actuator

摘要

A drive body 1, which is a piezoelectric element of bimorph type, is secured to a shaft 2. The shaft 2 is rotatably supported by a holder 12. A leaf spring 13 is fastened to the upper end of the holder 12. The leaf spring 13 is set in resilient contact with the upper end of the shaft 2. The friction between the shaft 2 and the leaf spring 13 acts as a rotation-suppressing force on the shaft 2. A sawtooth-waveform voltage is applied to the drive body 1 through a wire extending through the shaft 2 that has a hollow. When applied with the sawtooth-waveform voltage, the drive body 1 vibrates to the right and the left. The drive body 1 rotates around the shaft 2 in a specific direction, due to the difference in inertial force resulting from the difference in the deforming speed of the body 1. The voltage applied to the drive body 1 may linearly rises and falls repeatedly or may have a sinusoidal waveform. In either case, the voltage rises from a minimum value to a maximum value for time T1 and falls from the maximum value to the minimum value for time T2 that is different from time T1.