Improvement of servo robustness for digital sector servo system

In the smal I -sized magnetic hard disk drives the sector servo system is commmonly used for positioning control. The sector servo is a sampling servo and often its sampling period has to be longer than desired because of the data format structure. This long sampling period somet imes causes undesi red transient responses at seeking. In t his study the initial value compen- sation theory is applied to the sector servo. This compensation method is to input initial values, calculated by minimizing a performance index, into sett I ing servo compensators when the servo mode is switched from seeking to settling. Several experimental results show this method improves the servo performance.