A Simplified Dynamic Model for the Analysis of the Slider Off-Track Motion Due to Head-Disk Interactions

2007 ◽  
Author(s):  
Yanhui Yuan ◽  
Shao Wang
Keyword(s):  
Steady State ◽  
Dynamic Model ◽  
Rotational Speed ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Degree Of Freedom ◽  
Force Function ◽  
Transverse Displacement ◽  
Disk Drives ◽  
Rotational Mode

The slider off-track motion is a growing concern for hard disk drives with higher densities. In the present study, a five-degree-of-freedom model was developed for the analysis of the slider off-track motion. The situations of a slider in contact with a single bump and multiple bumps were studied. For a single bump, the excitation to the transverse displacement of the slider is close to an impulse. However, for multiple bumps in a sequence, the excitation gives an effect of a step force function with its plateau value dependent on the circumferential spacing of the bumps, and the rotational speed of the disk. In the case of a bump spacing of 50 μm and a rotational speed of 7200 rpm, the transverse displacement may reach a steady-state of more than 1 μm within 10 ms. The off-track motion of the slider is dominated by the rotational mode of the actuator arm and the sway mode of the suspension, and is very weakly affected by other modes.

A Nonlinear Feedback Control Scheme for Transient Performance Enhancement in Hard Disk Drives

2014 ◽  
Author(s):  
Minghui Zheng ◽  
Xu Chen ◽  
Masayoshi Tomizuka
Keyword(s):  
Steady State ◽  
Pid Controller ◽  
Control Algorithm ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drives ◽  
Transient Performance ◽  
Nonlinear Feedback ◽  
Nonlinear Pid Controller ◽  
Steady State Performance

This paper aims to develop a nonlinear control algorithm to break the limitations of linear PID controls and improve the transient performance during the short-span track seeking / settling in hard disk drives (HDDs). It is designed based on a baseline PID controller which is well-designed to obtain good track following performance. The control algorithm is a combination of a nonlinear PID controller and a nonlinear turbo controller (NTC): when the position error signal (PES) is large, NTC assists the nonlinear PID controller to rapidly reduce the error; when PES is small, NTC is turned off to avoid possible chattering and ensure good steady state performance. As PES becomes even smaller, the nonlinear PID controller is reduced to the baseline PID controller to keep good steady state performance.

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