Lifted Frequency-Domain Identification of Closed-Loop Multirate Systems: Applied to Dual-Stage Actuator Hard Disk Drives

Abstract

Frequency-domain representations are crucial for the design and performance evaluation of controllers in multirate systems, specifically to address intersample performance. The aim of this paper is to develop an effective frequency-domain system identification technique for closed-loop multirate systems using solely slow-rate output measurements. By indirect identification of multivariable time-invariant representations through lifting, in combination with local modeling techniques, the multirate system is effectively identified. The developed method is capable of accurate identification of closed-loop multirate systems within a single identification experiment, using fast-rate excitation and inputs, and slow-rate outputs. Finally, the developed framework is validated using a benchmark problem consisting of a multivariable dual-stage actuator from a hard disk drive, demonstrating its applicability and accuracy.

Figures (6)

• Figure 1: (Left:) Photograph of hard disk drive with dual-stage actuator, consisting of a VCM and a PZT actuator. (Right:) Schematic overview of hard disk drive with dual-stage actuator.
• Figure 2: Multirate feedback loop considered, where fast-rate system $P$ is to be identified.
• Figure 3: Feedback structure considered for identification of the PZT and VCM actuators $P_p$ and $P_v$ of the hard disk drive in Figure \ref{['CLMR:fig:HDD']}.
• Figure 4: The FRFs of $F_p$ ()and $F_v$ ()show that the filters suppress dynamics beyond the Nyquist frequency of the slow-rate output $y_l$ ().
• Figure 5: The developed lifted closed-loop identification technique with local rational modeling ()identifies the VCM $P_p(\Omega\xspace_{k})$ accurately, even beyond the Nyquist frequency of the slow-rate output $y_l$ ().

Theorems & Definitions (2)

• Remark 1
• Remark 2