B-1-3 Design of multi-layer coil actuator for hard disk drives

We proposed an actuator called a multi-layer coil actuator that attenuates an out-of-plane mode. The proposed actuator has film coil attached on VCM coil one above the other. Direction of pattern on the film coil above VCM coil is same as VCM coil, while that below VCM coil is opposite. Film coil doesn't generate rotational moment, but torsion moment. The ratio of the current for the film coil can be changed to attenuate an out-of-plane mode. We constructed the multi-layer coil actuator, and measured the frequency response from the current of the two coils to head displacement by different ratios of current of film coil. The effectiveness of the proposed actuator in reducing excitation of the coil torsion mode was demonstrated through experiment.