The design of load/unload algorithm for 2.5″ hard disk drive in SSTW process

To prevent striking of head to disc in servo track writing process, head velocity is controlled by ramp loading procedure for moving read/write head from ramp to disc surface properly. The author presents the approach to design load/unload algorithm for 2.5" hard disk drive in SSTW process. The 2 Degree of Freedom PID Control Structure has been applied instead of conventional PID for VCM velocity control. Furthermore; we use Characteristic Ratio Assignment Technique for adjusting PID parameters in order to obtain less overshoot in output response. The experimental results tested with self-servo track writer PH4LC unit have been shown that 2DOF PID algorithm can achieve the performance specification requirement and reducing HDI problem in load/unload control of 2.5" hard disk drive, efficiently.