Track Settling Control System to Reduce Residual Vibration during Track Seek of Magnetic Disk Drives.

In magnetic disk drives, several controllers switch from one to another to perform one servo action. These mode switching controllers provide fast access and accurate positioning. The requirement of faster seeking in magnetic disk drives propagates residual vibration during settling due to the mechanical resonance of the positioning system. We have developed a settling control mode designed to reduce the residual vibration caused by primary mechanical resonance. Our method consists of a closed loop design to stabilize the primary resonance by tuning the phase of the open loop transfer function without a notch filter and a design of controller initial values at settling start point. The method is more effective in reducing vibration compared to the conventional method using a notch filter because the transfer functions from the initial state variables of the primary resonance to the position of the actuator are significantly damped at the frequency of the primary resonance. Simulation and experimental results on transient characteristics in track seek show that the method provide fast and vibration-free settling on the target track.