Research On Key Technologies Of Hard Disk Servo Track Writing

In the whole process of production for a hard disk drive, the servo track writing is a very important process. In this process all servo information will be written in hard disk in a special format. In this paper, the format details of the hard disk drive servo information and its code will be given. And then the architecture of hard disk drive servo track writing system will be introduced and be analyzed.A new servo track writing method (named spiral servo track writing) for hard disks is introduced in this paper. In this method, at first some initial signal is written on the hard disk in spiral tracks, after that, all servo information will be filled in. By this method we can short the time taken on expensive servo track writing equipments and hence reduce the production costs.Among the method of controlling the motor of hard disk, we originally use the error between two zero cross of the back electromotive force to be the feedback signal to control the speed of the motor with close loop. But the precision is too low, aiming at this, the article design and achieve a new method that use the clock number read back from the clock head to be the feedback signal, and use the PID controller to control the axis motor of the hard disk on hardware flat. The article use FPGA to complement the PID compute and the picking up of the clock error signal. The simulating for this design proves it can achieve a high precision for controlling.