High-Bandwidth Servo Design for Shaping the Mechanical Resonance of the Actuator in Hard Disk Drives

In order to meet today's increasing performance demands on hard disk drives, the head positioning accuracy should be improved and the bandwidth must be increased. Accordingly, we developed a method for designing a high-bandwidth servo control system, in which the mechanical resonant mode is the bandwidth limitation. This method uses a simple 2nd-order filter in series with a conventional compensator for shifting the actuator's resonant mode to a higher frequency (we call this "resonance compensation"). By using this method, users can easily design the high-bandwidth servo controller without the need for complicated calculations involving matrices. We verified the effectiveness of this resonance-compensation method by designing an actual servo control system. and experimentally measuring its high bandwidth.