Sequential vs. Parallel Synthesis for Dual-Stage Hard Disk Drives

2012 ◽  
Author(s):  
Craig E. Stensland ◽  
Mark Bedillion
Keyword(s):  
Controller Design ◽  
Hard Disk Drives ◽  
Voice Coil Motor ◽  
Hard Disk ◽  
Parallel Synthesis ◽  
Disk Drives ◽  
Parallel Design ◽  
High Bandwidth ◽  
Dual Stage ◽  
Single Input

Modern hard disk drives (HDDs) use single-input, dual-output (SIDO) controllers to control a dual-stage plant consisting of a large-stroke voice coil motor (VCM) and a short-stroke, high-bandwidth piezoelectric microactuator (PZT). Various methods have been proposed to perform the SIDO controller design; among the most commonly used approaches is μ-synthesis. While μ-synthesis generates stable controllers for the overall system, it does not guarantee stability of the VCM-only loop in the presence of microactuator saturation or failure. One approach to the DISO design that maintains VCM-only stability is the sequential design of VCM and PZT controllers. This paper presents a systematic study of sequential vs. parallel design. Designs are evaluated by comparing values of μ obtained for equivalent designs between the sequential and parallel approaches. The circle criterion is used to test stability of the system under saturation. Performance of sequential and parallel designs in shock events are tested in simulation.

High-bandwidth controller design for dual-stage actuator system in hard disk drives

2022 ◽  
pp. 107754632110623
Author(s):  
Shota Yabui ◽  
Takenori Atsumi
Keyword(s):  
Controller Design ◽  
Hard Disk Drives ◽  
Voice Coil Motor ◽  
Hard Disk ◽  
Disk Drives ◽  
Positioning Accuracy ◽  
Micro Actuator ◽  
Dual Stage ◽  
Actuator System ◽  
Dual Stage Actuator

Large-capacity hard disk drives are important for the development of an information society. The capacities of hard disk drives depend on the positioning accuracy of magnetic heads, which read and write digital data, in disk-positioning control systems. Therefore, it is necessary to improve positioning accuracy to develop hard disk drives with large capacities. Hard disk drives employ dual-stage actuator systems to accurately control the magnetic heads. A dual-stage actuator system consists of a voice coil motor and micro-actuator. In micro-actuators, there is a trade-off between head-positioning accuracy and stroke limitation. In particular, in a conventional controller design, the micro-actuator is required to actuate such that it compensates for low-frequency vibration. To overcome this trade-off, this study proposes a high-bandwidth controller design for the micro-actuator in a dual-stage actuator system. The proposed method can reduce the required stroke of the micro-actuator by increasing the gain of the feedback controller of the voice coil motor at low frequencies. Although the voice coil motor control loop becomes unstable, the micro-actuator stabilizes the entire feedback loop at high frequencies. As a result, the control system improves the positioning accuracy compared to that achieved by conventional control methods, and the required micro-actuator stroke is reduced.

Dual-Stage Servo Control for an Optical Pointing System

2013 ◽  
Author(s):  
Eric D. Miller ◽  
Raymond A. de Callafon
Keyword(s):  
Power Consumption ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Single Stage ◽  
Servo Control ◽  
Disk Drives ◽  
Bandwidth Control ◽  
High Bandwidth ◽  
Dual Stage ◽  
Reduced Power Consumption

In the realm of hard disk drives (HDD), dual-stage servo control has been shown to achieve increased control bandwidth and reduced power consumption compared to single-stage architectures [1]–[4]. Motivated by these results, we seek to apply dual-stage control to an analogous case of an optical pointing system, which has similar objectives of high-bandwidth control over a wide spatial range.

Identification of Resonance Frequencies in Dual-Stage Hard Disk Drives: A Practical Strategy

2017 ◽  
Author(s):  
Minghui Zheng ◽  
Shiying Zhou ◽  
Masayoshi Tomizuka
Keyword(s):  
Hard Disk Drives ◽  
Control Process ◽  
Voice Coil Motor ◽  
Hard Disk ◽  
Disk Drives ◽  
Single Output ◽  
Main Challenge ◽  
Practical Strategy ◽  
Resonance Frequencies ◽  
Dual Stage

In hard disk drives (HDDs), there exist multiple mechanical resonances whose central frequencies may shift due to the change of environmental conditions such as the temperature. Such slowly varying resonance frequencies, if not handled properly, may degrade the positioning accuracy and even result in the instability of the closed-loop HDD system. Therefore, it is important to identify these resonance frequencies efficiently without interrupting the reading/writing process in HDDs. One main challenge of the frequency identification in a dual-stage HDD lies in the fact that it is a double-input-single-output (DISO) system. The outputs of the voice coil motor (VCM) and the piezoelectric microactuator (PZT) are coupled together. This paper proposes a practical strategy to identify the resonance frequencies in both the VCM and the PZT without disabling the PZT control process. Bandpass filters are utilized to separate the overall position error signal (PES) into several frequency segments based on priorly-known frequency range for each resonance. Two standard parameter adaptation algorithms are studied and discussed. Simulation results validate the effectiveness of proposed identification strategy.

Application of Mixed H2/H∞ Data Driven Control Design to Dual Stage Hard Disk Drives

2018 ◽  
Author(s):  
Omid Bagherieh ◽  
Prateek Shah ◽  
Roberto Horowitz
Keyword(s):  
Closed Loop ◽  
Transfer Functions ◽  
Hard Disk Drives ◽  
Control Design ◽  
Hard Disk ◽  
Data Driven ◽  
Disk Drives ◽  
Design Strategies ◽  
Data Driven Approach ◽  
Dual Stage

A data driven control design approach in the frequency domain is used to design track following feedback controllers for dual-stage hard disk drives using multiple data measurements. The advantage of the data driven approach over model based approach is that, in the former approach the controllers are directly designed from frequency responses of the plant, hence avoiding any model mismatch. The feedback controller is considered to have a Sensitivity Decoupling Structure. The data driven approach utilizes H∞ and H2 norms as the control objectives. The H∞ norm is used to shape the closed loop transfer functions and ensure closed loop stability. The H2 norm is used to constrain and/or minimize the variance of the relevant signals in time domain. The control objectives are posed as a locally convex optimization problem. Two design strategies for the dual-stage hard disk drive are presented.

Sign in / Sign up

Export Citation Format

Share Document