The Experts below are selected from a list of 4785 Experts worldwide ranked by ideXlab platform
Ben M Chen - One of the best experts on this subject based on the ideXlab platform.
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a Hard Disk Drive servo system design using composite nonlinear feedback control with optimal nonlinear gain tuning methods
IEEE Transactions on Industrial Electronics, 2010Co-Authors: Weiyao Lan, Chin Kwan Thum, Ben M ChenAbstract:This paper investigates the design of composite nonlinear-feedback (CNF) control law for a Hard-Disk-Drive (HDD) servo system. First, a scaled nonlinear function is introduced for the CNF control law, in which a parameter is scaled by the error between the amplitude of the target reference and the initial value of the system controlled output. The closed-loop system under the scaled function has robust transient performance to the variation of the amplitude of the target reference. Then, the parameters of the selected nonlinear function are tuned by optimal tuning methods. More specifically, the parameter-tuning problem is formulated as an optimization problem, which can be solved efficiently via numerical methods. The simulation and experimental results show that the control law designed using the new approach yields excellent performance for both track seeking and track following in the HDD servo system.
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modeling and compensation of nonlinearities and friction in a micro Hard Disk Drive servo system with nonlinear feedback control
IEEE Transactions on Control Systems and Technology, 2005Co-Authors: Kemao Peng, Ben M Chen, Guoyang Cheng, Tong Heng LeeAbstract:Friction and nonlinearities result in large residual errors and deteriorate the performance of head positioning of Hard Disk Drive (HDD) servo systems and other mechanical servo systems. Thus, it is highly desirable to characterize the behaviors of nonlinearities and friction in the servo systems. This paper presents a fairly comprehensive modeling and compensation of friction and nonlinearities of a typical voice-coil-motor (VCM) actuator used in commercial HDDs, and the design of an HDD servo system using an enhanced nonlinear control technique. Our contributions are two-fold: We will first obtain a complete model of the VCM actuator including friction and nonlinear characteristics through a careful examination of the configuration and structure of the actual system and through a thorough analysis of its physical effects together with its time-domain and frequency-domain responses. We will then proceed to design a servo system for the Hard Drive using an enhanced composite nonlinear feedback (CNF) control technique with a simple friction and nonlinearity compensation scheme. The enhanced CNF technique has a feature of removing the uncompensated portion of friction and nonlinearities without sacrificing the overall tracking performance. Simulation and experimental results for both the modeling and the servo design show that our approach is very effective and successful. In particular, our experimental results show that the enhanced CNF control has outperformed the conventional proportional-integral-derivative (PID) control in settling time by 76%. We believe that this approach can be adopted to solve other servomechanism problems.
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discrete time composite nonlinear feedback control with an application in design of a Hard Disk Drive servo system
IEEE Transactions on Control Systems and Technology, 2003Co-Authors: Venkatakrishnan Venkataramanan, Ben M Chen, Kemao Peng, Tong Heng LeeAbstract:In a typical Disk Drive servo system, two or more types of controllers are used for track seeking, track following, and track settling modes. This leads to the problem of mode switching among these controllers. We present in this paper a unified control scheme, the discrete-time composite nonlinear feedback control, which can perform all the above functions in Hard Disk Drive (HDD) servo systems with actuator saturation. The proposed scheme is composed by combining a linear feedback law and a nonlinear feedback law. The linear feedback law is designed to yield a fast response, while the nonlinear feedback law is used to increase the damping ratio of the closed-loop system as the system output approaches the command input. In the face of actuator saturation, this control law not only increases the speed of closed-loop response, but also improves the settling performance. Implementation results show that the proposed method outperforms the conventional proximate time-optimal servomechanism by about 30% in settling time.
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a new approach to the design of mode switching control in Hard Disk Drive servo systems
Control Engineering Practice, 2002Co-Authors: Venkatakrishnan Venkataramanan, Ben M Chen, Tong Heng Lee, Guoxiao GuoAbstract:In a modern large-capacity magnetic Hard Disk Drive (HDD), both fast track seeking and perfect positioning of the read/write head are required. Mode switching control (MSC) approaches are widely used to meet these requirements. This paper proposes a new approach in designing MSC with an application to HDD servo systems. The proposed scheme uses a proximate time-optimal servomechanism in the track seeking mode, and a robust perfect tracking (RPT) controller in the track following mode. Unlike the conventional MSC approaches, the new method does not require an initial value compensation during mode switching. This is because the RPT controller in the second stage is capable of rendering the Lp-norm ð1ppoNÞ of the resulting tracking error arbitrarily small in the presence of external disturbances and initial conditions. Simulation and experimental results show that the proposed method improves the seek and settling time by about 10% over the conventional approaches. r 2002 Elsevier Science Ltd. All rights reserved.
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Hard Disk Drive servo systems
2002Co-Authors: Ben M Chen, Tong Heng Lee, Kemao Peng, Venkatakrishnan VenkataramananAbstract:The second edition of this monograph provides a systematic treatment of the design of Hard Disk Drive servo systems updated to reflect recent improvements in spindle speed and bit density and other changes in this fast-moving field. In particular, it focuses on the applications of some newly developed results in control theory, i.e., robust and perfect tracking control and composite non-linear feedback control which are suitable for track following and seeking respectively. Emphasis is placed on Hard Disk Drive servo systems with single- or dual-stage actuation using a voice-coil-motor actuator enhanced in the latter case by the addition of a micro-actuator providing faster responses and therefore higher bandwidth in track following. Modeling and compensation of nonlinearities and friction in microDrives, disturbance rejection and resonance compensation are also addressed. The Linear Systems and CNF MATLAB toolkits used to develop many of the results can be downloaded from the book's website.
Mitsuru Igami - One of the best experts on this subject based on the ideXlab platform.
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mergers innovation and entry exit dynamics consolidation of the Hard Disk Drive industry 1996 2016
The Review of Economic Studies, 2020Co-Authors: Mitsuru Igami, Kosuke UetakeAbstract:How far should an industry be allowed to consolidate when competition and innovation are endogenous? We develop a stochastically alternating-move game of dynamic oligopoly and estimate it using data from the Hard Disk Drive industry, in which a dozen global players consolidated into only three in the last 20 years. We find plateau-shaped equilibrium relationships between competition and innovation, with heterogeneity across time and productivity. Our counterfactual simulations suggest the current rule-of-thumb policy, which stops mergers when three or fewer firms exist, strikes approximately the right balance between pro-competitive effects and value-destruction side effects in this dynamic welfare trade-off.
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estimating the innovator s dilemma structural analysis of creative destruction in the Hard Disk Drive industry 1981 1998
Journal of Political Economy, 2017Co-Authors: Mitsuru IgamiAbstract:This paper studies strategic industry dynamics of creative destruction in which firms and technologies experience turnover. Theories predict that cannibalization between existing and new products delays incumbents’ innovation, whereas preemptive motives accelerate it. Incumbents’ cost (dis)advantage relative to that of entrants would further reinforce these tendencies. To empirically assess these three forces, I estimate a dynamic oligopoly model using a unique panel data set of Hard Disk Drive manufacturers. The results suggest that despite strong preemptive motives and a substantial cost advantage over entrants, cannibalization makes incumbents reluctant to innovate, which can explain at least 57 percent of the incumbent-entrant innovation gap.
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mergers innovation and entry exit dynamics consolidation of the Hard Disk Drive industry 1996 2016
Social Science Research Network, 2016Co-Authors: Mitsuru Igami, Kosuke UetakeAbstract:How far should an industry be allowed to consolidate when competition and innovation are endogenous? We extend Rust's (1987) framework to incorporate a stochastically alternating-move game of dynamic oligopoly, and estimate it using data from the Hard Disk Drive industry, in which a dozen global players consolidated into only three in the last 20 years. We find plateau-shaped equilibrium relationships between competition and innovation, with systematic heterogeneity across time and productivity. Our counterfactual simulations suggest the optimal policy should stop mergers when five or fewer firms exist, highlighting a dynamic welfare tradeoff between ex-post pro-competitive effects and ex-ante value-destruction side effects.
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estimating the innovator s dilemma structural analysis of creative destruction in the Hard Disk Drive industry 1981 1998
2015Co-Authors: Mitsuru IgamiAbstract:This paper studies strategic industry dynamics of creative destruction in which firms and technologies experience turnover. Theories predict cannibalization between existing and new products delays incumbents’ innovation, whereas preemptive motives accelerate it. Incumbents’ cost (dis)advantage relative to that of entrants would further reinforce these tendencies. To empirically assess these three forces, I develop and estimate a dynamic oligopoly model using a unique panel dataset of Hard Disk Drive (HDD) manufacturers (1981–98). The results suggest that despite strong preemptive motives and a substantial cost advantage over entrants, cannibalization makes incumbents reluctant to innovate, which can explain at least 57% of the incumbent-entrant innovation gap. I then assess hypothetical policy interventions concerning broad patents and license fees, and find the industry’s welfare trajectory difficult to outperform.
Tong Heng Lee - One of the best experts on this subject based on the ideXlab platform.
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modeling and compensation of nonlinearities and friction in a micro Hard Disk Drive servo system with nonlinear feedback control
IEEE Transactions on Control Systems and Technology, 2005Co-Authors: Kemao Peng, Ben M Chen, Guoyang Cheng, Tong Heng LeeAbstract:Friction and nonlinearities result in large residual errors and deteriorate the performance of head positioning of Hard Disk Drive (HDD) servo systems and other mechanical servo systems. Thus, it is highly desirable to characterize the behaviors of nonlinearities and friction in the servo systems. This paper presents a fairly comprehensive modeling and compensation of friction and nonlinearities of a typical voice-coil-motor (VCM) actuator used in commercial HDDs, and the design of an HDD servo system using an enhanced nonlinear control technique. Our contributions are two-fold: We will first obtain a complete model of the VCM actuator including friction and nonlinear characteristics through a careful examination of the configuration and structure of the actual system and through a thorough analysis of its physical effects together with its time-domain and frequency-domain responses. We will then proceed to design a servo system for the Hard Drive using an enhanced composite nonlinear feedback (CNF) control technique with a simple friction and nonlinearity compensation scheme. The enhanced CNF technique has a feature of removing the uncompensated portion of friction and nonlinearities without sacrificing the overall tracking performance. Simulation and experimental results for both the modeling and the servo design show that our approach is very effective and successful. In particular, our experimental results show that the enhanced CNF control has outperformed the conventional proportional-integral-derivative (PID) control in settling time by 76%. We believe that this approach can be adopted to solve other servomechanism problems.
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discrete time composite nonlinear feedback control with an application in design of a Hard Disk Drive servo system
IEEE Transactions on Control Systems and Technology, 2003Co-Authors: Venkatakrishnan Venkataramanan, Ben M Chen, Kemao Peng, Tong Heng LeeAbstract:In a typical Disk Drive servo system, two or more types of controllers are used for track seeking, track following, and track settling modes. This leads to the problem of mode switching among these controllers. We present in this paper a unified control scheme, the discrete-time composite nonlinear feedback control, which can perform all the above functions in Hard Disk Drive (HDD) servo systems with actuator saturation. The proposed scheme is composed by combining a linear feedback law and a nonlinear feedback law. The linear feedback law is designed to yield a fast response, while the nonlinear feedback law is used to increase the damping ratio of the closed-loop system as the system output approaches the command input. In the face of actuator saturation, this control law not only increases the speed of closed-loop response, but also improves the settling performance. Implementation results show that the proposed method outperforms the conventional proximate time-optimal servomechanism by about 30% in settling time.
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a new approach to the design of mode switching control in Hard Disk Drive servo systems
Control Engineering Practice, 2002Co-Authors: Venkatakrishnan Venkataramanan, Ben M Chen, Tong Heng Lee, Guoxiao GuoAbstract:In a modern large-capacity magnetic Hard Disk Drive (HDD), both fast track seeking and perfect positioning of the read/write head are required. Mode switching control (MSC) approaches are widely used to meet these requirements. This paper proposes a new approach in designing MSC with an application to HDD servo systems. The proposed scheme uses a proximate time-optimal servomechanism in the track seeking mode, and a robust perfect tracking (RPT) controller in the track following mode. Unlike the conventional MSC approaches, the new method does not require an initial value compensation during mode switching. This is because the RPT controller in the second stage is capable of rendering the Lp-norm ð1ppoNÞ of the resulting tracking error arbitrarily small in the presence of external disturbances and initial conditions. Simulation and experimental results show that the proposed method improves the seek and settling time by about 10% over the conventional approaches. r 2002 Elsevier Science Ltd. All rights reserved.
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Hard Disk Drive servo systems
2002Co-Authors: Ben M Chen, Tong Heng Lee, Kemao Peng, Venkatakrishnan VenkataramananAbstract:The second edition of this monograph provides a systematic treatment of the design of Hard Disk Drive servo systems updated to reflect recent improvements in spindle speed and bit density and other changes in this fast-moving field. In particular, it focuses on the applications of some newly developed results in control theory, i.e., robust and perfect tracking control and composite non-linear feedback control which are suitable for track following and seeking respectively. Emphasis is placed on Hard Disk Drive servo systems with single- or dual-stage actuation using a voice-coil-motor actuator enhanced in the latter case by the addition of a micro-actuator providing faster responses and therefore higher bandwidth in track following. Modeling and compensation of nonlinearities and friction in microDrives, disturbance rejection and resonance compensation are also addressed. The Linear Systems and CNF MATLAB toolkits used to develop many of the results can be downloaded from the book's website.
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design and implementation of a Hard Disk Drive servo system using robust and perfect tracking approach
Conference on Decision and Control, 1999Co-Authors: T B Goh, Ben M Chen, Tong Heng Lee, Zhongming Li, Tony HuangAbstract:We tackle the problem of a servo system design for a conventional Hard Disk Drive with a single voice-coil-motor (VCM) actuator using the so-called robust and perfect tracking (RPT) approach. We first model the physical system and then formulate it into a robust and perfect tracking problem, in which a measurement feedback controller can be obtained to achieve a robust and perfect tracking for any step reference in the presence of external disturbances and arbitrarily initial conditions. Some trade-offs are then made in order for the RPT controller to be implementable using existing Hardware setup. The implementation results of the RPT controller are compared with those of a PID controller. The results show that the servo system with our RPT controller has much better performances than the PID one has. It has faster settling time, lower overshoots and higher accuracy.
Guoxiao Guo - One of the best experts on this subject based on the ideXlab platform.
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Hard Disk Drive mechatronics and control
2006Co-Authors: Abdullah Al Mamun, Guoxiao GuoAbstract:The Hard Disk Drive is one of the finest examples of the precision control of mechatronics, with tolerances less than one micrometer achieved while operating at high speed. Increasing demand for higher data density as well as disturbance-prone operating environments continue to test designers' mettle. Explore the challenges presented by modern Hard Disk Drives and learn how to overcome them with Hard Disk Drive: Mechatronics and Control.Beginning with an overview of Hard Disk Drive history, components, operating principles, and industry trends, the authors thoroughly examine the design and manufacturing challenges. They start with the head positioning servomechanism followed by the design of the actuator servo controller, the critical aspects of spindle motor control, and finally, the servo track writer, a critical technology in Hard Disk Drive manufacturing. By comparing various design approaches for both single- and dual-stage servomechanisms, the book shows the relative pros and cons of each approach. Numerous examples and figures clarify and illustrate the discussion.Exploring practical issues such as models for plants, noise reduction, disturbances, and common problems with spindle motors, Hard Disk Drive: Mechatronics and Control avoids heavy theory in favor of providing hands-on insight into real issues facing designers every day.
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Hard Disk Drive mechatronics and control
2006Co-Authors: Abdullah Al Mamun, Guoxiao Guo, Chao BiAbstract:INTRODUCTION History of HDD Technology Components of a Hard Disk Drive Accessing Data in HDD Trend in HDD Industry Alternative Recording Technologies HEAD POSITIONING SERVOMECHANISM The Servo Loop The Actuator Feedback of Position Signal High Frequency Dynamics Noise and Disturbances Track Seek Controller DESIGN OF ACTUATOR SERVO CONTROLLER Review of Design Methods PID-Type Control Factors Limiting Servo Performance Optimal Control Advanced Topics Emergence of Dual-Stage Actuator Control of Dual-Stage Actuator SPINDLE MOTOR CONTROL Magnetic Field Fundamentals Electric Motor Fundamentals Spindle Motors Used in HDD Spindle Motor Drive System SERVO TRACK WRITER Introduction HAD Servowriting Media STW Self Servowriting A Laboratory-Scale Example Printing the Patterns BIBLIOGRAPHY INDEX
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practical implementation of a neural network controller in a Hard Disk Drive
IEEE Transactions on Control Systems and Technology, 2005Co-Authors: Guido Herrmann, Guoxiao GuoAbstract:This brief gives a practical account of the application of an improved adaptive neural network (NN) controller to the voice-coil-motor (VCM)-actuator of a Hard Disk Drive (HDD). Necessary practical modifications are presented which allow the implementation of the controller for a VCM-actuator with high-frequency resonances. For resonance compensation, notch filter compensators are augmented while parameter estimation errors are counteracted by employing robust parameter estimation techniques. It is shown practically that this controller is a good candidate for a track seek/following controller in HDDs.
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a new approach to the design of mode switching control in Hard Disk Drive servo systems
Control Engineering Practice, 2002Co-Authors: Venkatakrishnan Venkataramanan, Ben M Chen, Tong Heng Lee, Guoxiao GuoAbstract:In a modern large-capacity magnetic Hard Disk Drive (HDD), both fast track seeking and perfect positioning of the read/write head are required. Mode switching control (MSC) approaches are widely used to meet these requirements. This paper proposes a new approach in designing MSC with an application to HDD servo systems. The proposed scheme uses a proximate time-optimal servomechanism in the track seeking mode, and a robust perfect tracking (RPT) controller in the track following mode. Unlike the conventional MSC approaches, the new method does not require an initial value compensation during mode switching. This is because the RPT controller in the second stage is capable of rendering the Lp-norm ð1ppoNÞ of the resulting tracking error arbitrarily small in the presence of external disturbances and initial conditions. Simulation and experimental results show that the proposed method improves the seek and settling time by about 10% over the conventional approaches. r 2002 Elsevier Science Ltd. All rights reserved.
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development of a multi channel pc based Hard Disk Drive bode plot generator
Asian Test Symposium, 1998Co-Authors: Kin Wee Choo, Guoxiao Guo, B M ChenAbstract:A five-channel generator is developed to obtain the frequency response of a Hard Disk Drive (HDD) by emulating the Bode-plot functions of a dynamic signal analyser (DSA). Written in LabVIEW, it runs on the Windows 95 platform using a standard Wintel PC, a commercial data acquisition (DAQ) board and an external Hardware anti-alias filter board. This generator achieves a superior advantage at lower cost through its ability to evaluate the track-following servo loop frequency response of up to five HDDs simultaneously. Besides reducing test-time and providing a degree of accuracy comparable to a commercial DSA, it also includes an option to save all acquired data to Disk for further analysis with other software engineering packages.
Yangquan Chen - One of the best experts on this subject based on the ideXlab platform.
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fractional order proportional derivative controller synthesis and implementation for Hard Disk Drive servo system
IEEE Transactions on Control Systems and Technology, 2014Co-Authors: Ying Luo, Tao Zhang, Bongjin Lee, Changik Kang, Yangquan ChenAbstract:In this brief, a fractional-order (FO) proportional derivative (PD) controller is designed in a systematic way based on the frequency responses data model for the Hard-Disk-Drive (HDD) servo system. The open-loop system using the designed FO controller is with a flat-phase feature around the gain crossover frequency, which obtains the robustness to loop-gain variations. Thus, the control performance can be made uniform with more consistency than the optimized traditional integer-order controller when the loop gain changes. The theoretical foundation of the FO controller design is presented first. Thereafter, the implementation details of the designed controller in the real-time HDD servo system are introduced, which are important for the real applications of the FO controllers in practice. From the experimental validation, the presented FO-PD controller and the design synthesis are found to be efficient in improving the track-following control performance for the HDD servo system.
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iterative learning control and repetitive control in Hard Disk Drive industry a tutorial
International Journal of Adaptive Control and Signal Processing, 2008Co-Authors: Yangquan Chen, Kevin L Moore, Jie Yu, Tao ZhangAbstract:This paper presents a tutorial on iterative learning control (ILC) and repetitive control (RC) techniques in Hard Disk Drive (HDD) industry for compensation of repeatable runouts (RRO). After each tutorial, an application example is given. For ILC, a simple filtering-free implementation for written-in RRO compensation is presented. For the RC part, a new application of RC in dual-stage HDD servo is presented. Copyright © 2007 John Wiley & Sons, Ltd.
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iterative learning control and repetitive control in Hard Disk Drive industry a tutorial
Conference on Decision and Control, 2006Co-Authors: Yangquan Chen, Kevin L Moore, Jie Yu, Tao ZhangAbstract:This paper presents a tutorial on iterative learning control (ILC) and repetitive control (RC) techniques in Hard Disk Drive (HDD) industry for compensation of repeatable runouts (RRO). After each tutorial, an application example is given. For ILC, a simple filtering-free implementation for written-in RRO compensation is presented. For the RC part, a new application of RC in dual stage HDD servo is presented. Finally, the widely used adaptive feedforward control (AFC) technique is explained from ILC point of view with discussions on challenges and issues in implementation in HDD industry.
