Measurement and modelling of disturbances in a servo track writer and advanced loop shaping to achieve higher track density

In this paper we present the idea of hybrid servo track writing and give a complete description of the developed hybrid servo track writer platform including its main functions and servo mechanism. The major disturbances and noise level in media-level servo track writing are identified based on the position error signal measured on the hybrid servo track writer platform. A dual-stage servo system, which is applicable in servo writing, is proposed and implemented on the experimental platform. With the disturbances and noise models, an advanced loop-shaping scheme based on Kalman—Yakubovic—Popov lemma is used to optimize the controller for the micro-actuator servo loop. The experimental results show that the tracking accuracy can reach 6 nm, which is able to support a track density of more than 400 000 tracks per inch.

[1]  Guido Herrmann,et al.  Practical implementation of a neural network controller in a hard disk drive , 2005, IEEE Transactions on Control Systems Technology.

[2]  Branislav Hredzak,et al.  Investigation of the effect of hard disk drive unbalance on repeatable and nonrepeatable runout , 2003, The Fifth International Conference on Power Electronics and Drive Systems, 2003. PEDS 2003..

[3]  Youyi Wang,et al.  Phase lead peak filter method to high TPI servo track writer with microactuators , 2006, 2006 American Control Conference.

[4]  H. Hindi,et al.  Rejecting oscillatory, non-synchronous mechanical disturbances in hard disk drives , 2001 .

[5]  Lihua Xie,et al.  A generalized KYP lemma based control design and application for 425 kTPI servo track writing , 2006, 2006 American Control Conference.

[6]  Chunling Du,et al.  Radial error propagation issues in self servo track writing technology , 2002 .

[7]  Yukihiro Uematsu,et al.  Development of the pushpin free STW [servo track writer] , 2001 .

[8]  Lihua Xie,et al.  $H_2$ Control for Head Positioning in Axial and Radial Dimensions for Self-Servo Track Writing , 2008, IEEE Transactions on Control Systems Technology.

[9]  H. T. Ho,et al.  Distortion effects on servo position error transfer function , 1997 .

[10]  R. Ehrlich,et al.  Major HDD TMR sources and projected scaling with TPI , 1999 .

[11]  Bucknell C. Webb,et al.  A self-servowrite clocking process , 2001 .

[12]  Terril Hurst,et al.  of the PES Pareto Method for Decomposing Baseline Noise Sources in Hard Disk Position Error Signals , 1998 .

[13]  K. Taniguchi,et al.  Development of the pushpin free STW , 2000, 2000 Asia-Pacific Magnetic Recording Conference. Digests of APMRC2000 on Mechanical and Manufacturing Aspects of HDD (Cat. No.00EX395).

[14]  Shuzhi Sam Ge,et al.  Hard Disk Drives Control in Mobile Applications , 2007, J. Syst. Sci. Complex..

[15]  Yukihiro Uematsu,et al.  Hard disk drive servo technology for media-level servo track writing , 2003 .

[16]  R. Horowitz,et al.  Vibration control of a PZT actuated suspension dual-stage servo system using a PZT sensor , 2002, Digest of the Asia-Pacific Magnetic Recording Conference.