A Novel Method Containing the Radial Error Propagation in Self-Servowriting in Hard Disk

Servo information can be used to tell the relative position of the magnetic head and data track. So it must be written in the manufacture process of hard disk drive (HDD). But traditional servo information writing process needs the help of servo track writer and the use of clean room. These cost a lot to HDD manufacture. The rapid increasing track density also compacts much to the servo information writing process. Self-servowriting process can use the equipments of HDD to implement the process of writing servo information. It can improve the productive efficiency of HDD manufacture. The process of self-servowriting and the problem that is critical to self-servowriting are discussed. The principle of self-servowriting and the phenomenon of radial error propagation are analyzed. Radial error propagation is caused by noise disturbance, “seed” track defect and deep reliance on last track shape. Then two different methods which could contain the error propagation are compared and their shortcomings are also discussed. Next, a new weighted correction signal method is described in details. Its effectiveness and advantage are proved in theory and in simulation test. The simulation shows it could decrease track absolute radial error and relative radial error simultaneously.