A repetitive process approach to the control of self-servowriting in disk drives

This paper considers the control problem for self-servowriting in disk drives where information propagation occurs in two independent directions, i.e. time and track number respectively. The resulting state-space model is not of the well known Roesser or fornasini-marchesini types and hence cannot be analyzed using the theory associated with these 2D discrete linear systems models. Instead, it is shown here that it can written as a discrete linear repetitive process state-space model which is an extension of those already encountered and for which it is necessary to develop new tools for stability analysis and controller design. Finally, the application of these is illustrated by a simulation example using industry supplied data.