Repeatable Runout Of Hard Disk Drive And Its Estimating Method Research

In computer system, hard disk drive (HDD) is indispensable storage equipment. HDD is widely used in digital video player, automobile, camera and so on. The capacity of magnetic disk drive has increased significantly in recent years, while the size of disk drive is keeping smaller and smaller. With rapid increase in track density, in track-following mode, the head positioning servo control loop must precisely positions the head on the desired track under various disturbance. The RRO (Repeatable Runout) has great influence in all disturbances. Considering this result, it is important to reduce the influence of the RRO to precisely control. After the source and characteristic of the RRO were analyzed, an improved estimating method to collect RRO disturbance data is proposed, and an experimental study was given for the proposed method.The main topics include in estimating RRO disturbance are the structure and principle of HDD, the magnetic recording theory, positioning error signal, and the servo information technology of HDD. The model, estimating and collecting methods of the RRO disturbance have been analyzed.Based on a simplified model of a HDD servo system, average method has been studied and improved. Approaches and calculational formulae of the estimating method of the RRO disturbance have been proposed. The RRO disturbance has been estimated on the 3000th track of a microdrive according to the proposed method.The improved estimating method is simple and has less computation burden. And this method is a favorable tool for research on new servo track writing technology and fast algorithm about position error signal estimation too.