A mode-switching control for motion control and its application to disk drives: design of optimal mode-switching conditions

The mode switching control (MSC) is a kind of variable-structure control system with switching in only one direction. When the mode is switched from the fast-movement servo mode to the precise-positioning servo mode, the switching time is the initial time when the precise-positioning mode begins. As a result, initial value compensation (IVC), a method that takes into account the initial state values, can be applied. We (1996) previously proposed the design of IVC and showed its effectiveness in disk drive servo controls. In this paper, a design method for determining the optimal combination of initial states for mode switching is proposed. Here, the H₂ norm of the transfer function between the initial values and the control input is defined as the performance index of the transient response after mode switching. By combining the IVC method with this method of determining the optimal switching conditions, the issues of mode switching are resolved. Several experimental results show the effectiveness of these methods