Digital Control Of Repetitive Errors In Disk Drive Systems

Tracking errors in disk drive systems have a significant repetitive component that is not explicitly taken into account in conventional servo controllers. Three specialized digital controllers applied as plug-in modules to a winchester disk drive with a pre-existing analog feedback controller to demonstrate their efficacy in the reduction of this periodic component. These controllers include the discrete time repetitive controller which is based on the internal model principle and feedforward cancellation controllers based on an adaptive prediction algorithm and on input and output measurements of the system.