Improvement of settling response of disk drive head positioning servo using mode switching control with initial value compensation

A Mode Switching Control (MSG) design method for disk drive head positioning servo is proposed. The MSC includes several controllers and switches from one to the other to achieve both precise positioning and short seek time requirements. The issue is "settling", the transient state after switching. This paper proposes the initial value compensation (IVC) method to improve transient characteristics after switching. Under the IVC method, certain values are placed in the state variables of the controller or an additional input is added at switching. From experimental data, we have proved that IVC reduces overshoot and slow transient response after switching. Also this IVC method does not affect any closed loop characteristics such as stability.