Control of transient response on a servosystem using mode-switching control, and its application to magnetic disk drives

Abstract

In many servosystems, fast movement and precise positioning are required. A mode-switching control (MSC) method, which has at least two controllers designed for fast or precise specifications, respectively, and switches from one controller to the other, has been proposed and widely used to meet these requirements. The issue raised by the use of this technique is the transient response after switching. This paper proposes a new control method to shape the transient response. This method gives an additional input to a controller just after mode switching. The additional input, which is an impulse response of the initial state variables of the plant at mode switching, is designed to change transfer functions from the initial variables to the controlled variables, such as position, into better ones with assigned poles. In experiments using hard disk drives, it is proved that this technique improves the transient responses after switching.