Design of P and PI controllers for head positioning in hard disk drives with time delay

Abstract

In today’s high performance positioning applications, due to stringent design objectives, it is very challenging to cope with input-output time delays. In Hard Disk Drive (HDD) servo system, the information flow between process and the controller is under a time delay. Typical state-space based modern control algorithms are not applicable to such infinite dimensional plants. In this thesis several control design objectives are considered and various types of stabilizing controllers are derived for this infinite dimensional plant. The objective of this thesis is to determine alternative simple (low order) controllers to the previously designed H∞ controller and controllers designed from Pade approximations. For this purpose, six different P and P I controllers for the unstable infinite dimensional plant are obtained. Comparisons of the controllers with each other are done and advantages of every approach are demonstrated.