Stretching servo performances on a spin stand

To support a higher track recording density for future generation magnetic recording systems on a conventional spin stand, good servo controllers and high-bandwidth actuators are needed. We add an additional sub-stage piezo actuator with sub-nm resolution to an existing spin stand system. The combination of a frequency-encoded servo pattern and a simplified decoding scheme is applied to generate the position error signal (PES) by means of an external PC-based servo system. Various servo control techniques, namely, PID control, near-perfect modeling (NPM) low-hump design, low hump H/sub /spl infin// control and feed-forward RRO compensation are designed and implemented on the same platform. Control performance comparison is then made and the experimental results show that PES 3/spl sigma/ is improved by up to 23.7% with the low-hump design together with the feed-forward RRO compensation.