Servo Controller Design for Triple-Stage Actuator in HDD to Compensate for High-Frequency Fan Vibration

Hard disk drives (HDDs) used for data servers are exposed to various vibrations. These vibrations mainly caused by the cooling fan that controls temperature inside server. The vibration affects positioning accuracy of magnetic heads read/write digital data. This is an obstacle obtaining high transfer rates. To compensate vibration, control system must have higher frequency bandwidth as spectra these peaks up 10 kHz. In current HDDs, a triple-stage consisting voice coil motor (VCM), milliactuator, and microactuator. this article, we propose design strategy vibration. addresses unstable controllers in system. gain feedback VCM milliactuators increased expand bandwidth. Although loops become due increase controller gain, microactuator designed stabilize overall loop. As result, achieves performance proposed calculated based on compensation can improve approximately 48%–58% compared with conventional design.