Design of carriage with two-layer coils for hard disk drive actuator

We proposed a carriage called a two-layer coil carriage that attenuates an out-of-plane mode. The coil of the proposed carriage is divided into two parts that are stacked on one another. The ratio of the current for the two coils can be changed by optimizing the coil coefficients. We have clarified the mechanism of excitation of the out-of-plane mode. We constructed the two-layer coil carriage, and measured the frequency response from the voice coil motor current of the two coils to head displacement. The effectiveness of the proposed carriage in reducing excitation of the coil torsion mode was demonstrated through simulation and experiment.