Design and Implementation of Feedback Resonance Compensator in Hard Disk Drive Servo System: A Mixed Passivity, Negative
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Design and Implementation of Feedback Resonance Compensator in Hard Disk Drive Servo System: A Mixed Passivity, Negative-Imaginary and Small-Gain Approach in Discrete Time Md. Arifur Rahman1 · Abdullah Al Mamun1 · Kui Yao2 · Sajal K. Das1
Received: 21 October 2014 / Revised: 1 April 2015 / Accepted: 20 April 2015 © Brazilian Society for Automatics–SBA 2015
Abstract This paper presents a feedback resonance compensator designed in a simple and yet efficient way to suppress the effects of resonant modes of voice coil motor actuator used in hard disk drive (HDD) servo system. A velocity feedback controller is chosen as the feedback resonance compensator. Resonant modes of the actuator prohibit bandwidth to be pushed to higher frequencies and it causes large oscillations to the closed-loop system response. Therefore, effective compensation of mechanical resonant modes is one of the design challenges in HDD servomechanism. The proposed design is based on a mixed passivity, negative-imaginary and small-gain approach in discrete time which results in a robust stable controller. Firstly, stability of discrete-time interconnected system is analyzed using mixed passivity, negative-imaginary and small-gain properties. These results are analogous to previously established continuous-time case. Nowadays most of the control design is done in discrete time. Hence, this paper provides a base for discretization of mixed system with passivity, negativeThis work is supported by the Singapore National Research Foundation (NRF) under CRP Award No. NRF-CRP-4-2008-06 and IMRE/10-1C0107.
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Md. Arifur Rahman [email protected] Abdullah Al Mamun [email protected] Kui Yao [email protected] Sajal K. Das [email protected]
1
Department of ECE, National University of Singapore, Singapore, Singapore
2
A*STAR Institute of Materials Research and Engineering (IMRE), Singapore, Singapore
imaginary and small-gain properties. Secondly, a velocity feedback controller for resonance compensation is designed using this mixed approach. Simulation and experimental results substantiate the effectiveness of the controller. Keywords VCM · Velocity feedback controller · Passivity · Negative-imaginary · Small-gain · Discrete time · Stability
1 Introduction The magnetic components, i.e., the media and the head of a hard disk drive (HDD) are the major components that enable storage and writing or retrieval of binary information. Data bits are stored in concentric data tracks on a rotating disk coated with magnetic media. The read/write head (R/W head) fabricated on a single piece of slider is used for recording as well as retrieving data bits. The slider is positioned on the tracks by a head-positioning servomechanism. The head is controlled to move from one track to another track in minimum possible of time and then it is maintained as close to the center of the track as possible. Nowadays, HDD servomechanism uses dual-stage actuation which consists of a voice coil motor (VCM) and a piezoelectric secondary actuator (PSA). The VCM is used to provide
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