Comparison of the control performance for the following control system in HDDs

HDDs are necessary as an information storage equipment of the information technology devices. Since the application of HDDs expands by adjusting the digitization, the requirement for miniaturization and capacity enlargement of HDDs heighten. The areal density is defined as a multiplication of track density and linear density. With rapid increase in areal density, the head positioning servo controller must be precisely performed on the desired track against various disturbances caused by the dynamics of mechanical systems in track-following mode. In the track-following mode, the non-circular track path and the eccentricity of the spindle will cause RRO, and the disk vibration and pivot friction that is one of a force disturbance will cause the non-repeatable run-out (NRRO). Varied models have been proposed to represent the dynamic behavior of pivot friction. The authors propose a precise following control technique that is suppressing the effect of pivot friction by using high precision friction model. The paper compares the control performance with a proposed method and a conventional method such as a disturbance observer. The effectiveness of the proposal technique was verified by using HDDs head positioning control system.