It is known to the public that a piezoelectric device is used as an actuator. For example, a piezoelectric device has begun to be used as an actuator configured to drive a magnetic head of a hard disk drive. Normally, the head is fixed to a rotatable arm and, when the arm is rotated by a voice coil motor (VCM), the head is moved to a desired position on the disk. In recent years, in order to enhance the accuracy in positioning, a dual-stage actuator in which another accurate drive mechanism is added in the vicinity of the magnetic head separately from the VCM configured to drive the whole arm has been developed. A microactuator serving as the second stage is added to a distal end of the arm of the VCM serving as the first stage. A piezoelectric device is mounted on the suspension and, by applying a voltage to the piezoelectric device, the piezoelectric device expands or contracts to displace the magnetic head attached to the distal end of the suspension in the track direction.
Each of the piezoelectric devices varies in gain/voltage characteristics and, in order to accurately drive the actuator utilizing the piezoelectric device, it is necessary to measure the gain for each device to adjust the drive voltage. The gain of the piezoelectric device has voltage dependence, and hence it is necessary to obtain the gain by exciting the piezoelectric device by using a voltage that's actually used (on-track state). However, in general, the voltage of the on-track state is small, and hence the amplitude of the piezoelectric device is also small, and the measurement accuracy of the gain becomes poor. In order to improve the measurement accuracy, there arises the need to carry out measurement a plurality of times, and average the measurement results, and hence the overall measurement requires a lot of time.
In the conventional piezoelectric device drive apparatus, in order to compensate for the variation in gain, and improve the positioning accuracy, there has been a problem that the measurement of the gain takes a long time.