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Papers by Roberto HOROWITZ
Journal of Dynamic Systems Measurement and Control-transactions of The Asme, Nov 1, 2005
Volume 3: Modeling and Validation; Multi-Agent and Networked Systems; Path Planning and Motion Control; Tracking Control Systems; Unmanned Aerial Vehicles (UAVs) and Application; Unmanned Ground and Aerial Vehicles; Vibration in Mechanical Systems; Vibrations and Control of Systems; Vibrations: M..., 2018
A data driven control design approach in the frequency domain is used to design track following f... more 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.
Proceedings of the 2004 American Control Conference, 2004
Instrumenting a disk drive suspension with vibration sensing strain gages can enhance vibration s... more Instrumenting a disk drive suspension with vibration sensing strain gages can enhance vibration suppression in hard disk drives, provided that the gages are properly located and are sufficiently sensitive. The cost function of an optimal LQG controller with Kalman filter is proposed as an objective function for determining the optimal location and orientation of displacement sensors on a flexible structure, such as the placement of strain gages on a disk drive suspension. Analytical bounds are derived for the Kalman filter Riccati equation in a modal system with large sensor noise. These bounds produce analytical approximations that reduce the computational complexity of the LQG optimization approach with cheap control. Results are applied to a prototype disk drive suspension to identify sensor positions and sensor requirements. Methods of installing strain gages on steel at precise locations are briefly discussed.
IFAC Proceedings Volumes, 2011
ASME 2008 Dynamic Systems and Control Conference, Parts A and B, 2008
ASME 2009 Dynamic Systems and Control Conference, Volume 2, 2009
This paper discusses the design and implementation of two track-following controllers for dual-st... more This paper discusses the design and implementation of two track-following controllers for dual-stage hard disk drive servo systems. The first controller is designed by combining an outer loop sensitivity-decoupling (SD) controller with an inner loop disturbance observer (DOB). The second is designed by combining mixed H2/H∞ synthesis techniques with an add-on integral action. The designed controllers were implemented and evaluated on a disk drive with a PZT-actuated suspension-based dual-stage servo system. Position error signal (PES) for the servo system was obtained by measuring the slider displacement with an LDV and injecting a simulated track runout.
This paper discusses the design and implementation of H2 guaranteed cost control for dual-stage h... more This paper discusses the design and implementation of H2 guaranteed cost control for dual-stage hard disk drive track-following servo systems. The proposed approach is based on H2 guaranteed cost analysis, in which an upper bound on the worst-case H2 performance of a discrete-time system with gain-bounded unstructured uncertainty is determined via several Riccati equations. Subsequently, the output feedback H2 guaranteed cost control synthesis algorithm is presented by exploiting Riccati equation structure to reduce the number and complexity of the semi-definite programs (SDPs) that need to be solved. The presented control synthesis methodology is then applied to a hard disk drive with a PZT-actuated suspension. Experimental results on the actual disk drive validate our control design.
2006 American Control Conference, 2006
ASME 2008 Dynamic Systems and Control Conference, Parts A and B, 2008
In this paper, we present a new algorithm for solving the LQG control problem with variance const... more In this paper, we present a new algorithm for solving the LQG control problem with variance constraints which utilizes derivative information about the relevant ℋ2 costs to achieve quasi-Newton convergence. Using a lifting procedure, this algorithm is then generalized to work with linear periodically time-varying systems. This algorithm is then applied to the design of controllers for hard disk drives in order to assess the limits of performance of a particular setup. It is demonstrated that just by utilizing multirate sampling and actuation characteristics (i.e. without changing the hardware), the performance of this particular setup can improved by more than 39%.
Proceedings of the 2011 American Control Conference, 2011
IFAC Proceedings Volumes, 2008
State of the art high speed color printers require sheets being accurately positioned as they arr... more State of the art high speed color printers require sheets being accurately positioned as they arrive to the image transfer station (ITS). This goal has been achieved by constructing a steerable nips mechanism, which is located upstream from the ITS. This mechanism consists of two rollers which not only rotate to advance the paper along the track, but also steer the paper in the yaw direction. A recently developed nonlinear control strategy for the position of the sheet is briefly reviewed. The core of this paper focuses on the addition of a nonlinear observer used to estimate the longitudinal, lateral, and angular positions of a sheet, by detecting its motion along two of its perpendicular sides. The success of the approach presented is corroborated through simulations, in which the estimates from the extended Luenberger observer designed are used on a nonlinear feedback control strategy.
2008 American Control Conference, 2008
Dual-stage servo systems have been proposed as a method for attaining increased bit densities fro... more Dual-stage servo systems have been proposed as a method for attaining increased bit densities from computer hard disk drives. To aid in controller operation, the second-stage microactuator used in a dual-stage system should operate at low voltages, feature relative position sensing, and have dynamics that interact well with the dynamics of the original drive servo. This paper describes a high-aspect ratio electrostatic microactuator modified to improve dynamic interactions, relative position sensor performance, and device yield. A multi-rate, multivariable control design technique was used to evaluate the closedloop performance of a disk drive system with a microactuator and relative position sensing. Closed-loop simulations reveal that the proposed configuration can reduce off-track position error. Addressing both hardware design and control design, this paper demonstrates the success of an integrated mechatronic approach to hard disk drive servo control.
6th IFAC Symposium on Mechatronic Systems, 2013, 2013
Volume 1: Active Control of Aerospace Structure; Motion Control; Aerospace Control; Assistive Robotic Systems; Bio-Inspired Systems; Biomedical/Bioengineering Applications; Building Energy Systems; Condition Based Monitoring; Control Design for Drilling Automation; Control of Ground Vehicles, Man..., 2014
In this paper we employ a modified filtered-x least mean squares (MFX-LMS) method to synthesis an... more In this paper we employ a modified filtered-x least mean squares (MFX-LMS) method to synthesis an adaptive repetitive controller for rejecting periodic disturbances at selective frequencies. We show how a MFX-LMS algorithm can be utilized when the reference signal is deterministic and periodic. A new adaptive step size is proposed with the motivation to improve the convergence rate of the MFX-LMS algorithm and fade the steady state excess error caused by the variation of estimated parameters in a stochastic environment. A novel secondary path modeling scheme is proposed to compensate for the modeling mismatches online. We further discuss the application of this adaptive controller in hard disk drives that use Bit Patterned Media Recording. Finally we present the results of comprehensive realistic numerical simulations and experimental implementations of the algorithms on a hard disk drive servo mechanism that is subjected to periodic disturbances known as repeatable runout.
2014 Conference on Information Storage and Processing Systems, 2014
2013 10th IEEE International Conference on Control and Automation (ICCA), 2013
Journal of Dynamic Systems, Measurement, and Control, 2006
In this paper we discuss the controller design of a PZT-actuated suspension dual-stage servo syst... more In this paper we discuss the controller design of a PZT-actuated suspension dual-stage servo system in hard disk drives. The proposed control structure includes an active vibration damping control loop and a track-following control loop. The vibration damping control loop, which runs at a faster rate than the track-following control loop, utilizes a PZT element on a PZT-actuated suspension as a vibration sensor to damp the resonance modes of the voice coil motor (VCM) and the PZT actuator. The vibration damping controller is designed using Kalman filter based state feedback control techniques. A simple dual-stage track-following controller is designed, based on the damped actuator model, using the sensitivity function decoupling design method. Simulation and experimental results are presented to demonstrate the benefits of this control scheme in expanding servo control bandwidth and suppressing airflow excited structural vibrations.
Journal of Dynamic Systems Measurement and Control-transactions of The Asme, Nov 1, 2005
Volume 3: Modeling and Validation; Multi-Agent and Networked Systems; Path Planning and Motion Control; Tracking Control Systems; Unmanned Aerial Vehicles (UAVs) and Application; Unmanned Ground and Aerial Vehicles; Vibration in Mechanical Systems; Vibrations and Control of Systems; Vibrations: M..., 2018
A data driven control design approach in the frequency domain is used to design track following f... more 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.
Proceedings of the 2004 American Control Conference, 2004
Instrumenting a disk drive suspension with vibration sensing strain gages can enhance vibration s... more Instrumenting a disk drive suspension with vibration sensing strain gages can enhance vibration suppression in hard disk drives, provided that the gages are properly located and are sufficiently sensitive. The cost function of an optimal LQG controller with Kalman filter is proposed as an objective function for determining the optimal location and orientation of displacement sensors on a flexible structure, such as the placement of strain gages on a disk drive suspension. Analytical bounds are derived for the Kalman filter Riccati equation in a modal system with large sensor noise. These bounds produce analytical approximations that reduce the computational complexity of the LQG optimization approach with cheap control. Results are applied to a prototype disk drive suspension to identify sensor positions and sensor requirements. Methods of installing strain gages on steel at precise locations are briefly discussed.
IFAC Proceedings Volumes, 2011
ASME 2008 Dynamic Systems and Control Conference, Parts A and B, 2008
ASME 2009 Dynamic Systems and Control Conference, Volume 2, 2009
This paper discusses the design and implementation of two track-following controllers for dual-st... more This paper discusses the design and implementation of two track-following controllers for dual-stage hard disk drive servo systems. The first controller is designed by combining an outer loop sensitivity-decoupling (SD) controller with an inner loop disturbance observer (DOB). The second is designed by combining mixed H2/H∞ synthesis techniques with an add-on integral action. The designed controllers were implemented and evaluated on a disk drive with a PZT-actuated suspension-based dual-stage servo system. Position error signal (PES) for the servo system was obtained by measuring the slider displacement with an LDV and injecting a simulated track runout.
This paper discusses the design and implementation of H2 guaranteed cost control for dual-stage h... more This paper discusses the design and implementation of H2 guaranteed cost control for dual-stage hard disk drive track-following servo systems. The proposed approach is based on H2 guaranteed cost analysis, in which an upper bound on the worst-case H2 performance of a discrete-time system with gain-bounded unstructured uncertainty is determined via several Riccati equations. Subsequently, the output feedback H2 guaranteed cost control synthesis algorithm is presented by exploiting Riccati equation structure to reduce the number and complexity of the semi-definite programs (SDPs) that need to be solved. The presented control synthesis methodology is then applied to a hard disk drive with a PZT-actuated suspension. Experimental results on the actual disk drive validate our control design.
2006 American Control Conference, 2006
ASME 2008 Dynamic Systems and Control Conference, Parts A and B, 2008
In this paper, we present a new algorithm for solving the LQG control problem with variance const... more In this paper, we present a new algorithm for solving the LQG control problem with variance constraints which utilizes derivative information about the relevant ℋ2 costs to achieve quasi-Newton convergence. Using a lifting procedure, this algorithm is then generalized to work with linear periodically time-varying systems. This algorithm is then applied to the design of controllers for hard disk drives in order to assess the limits of performance of a particular setup. It is demonstrated that just by utilizing multirate sampling and actuation characteristics (i.e. without changing the hardware), the performance of this particular setup can improved by more than 39%.
Proceedings of the 2011 American Control Conference, 2011
IFAC Proceedings Volumes, 2008
State of the art high speed color printers require sheets being accurately positioned as they arr... more State of the art high speed color printers require sheets being accurately positioned as they arrive to the image transfer station (ITS). This goal has been achieved by constructing a steerable nips mechanism, which is located upstream from the ITS. This mechanism consists of two rollers which not only rotate to advance the paper along the track, but also steer the paper in the yaw direction. A recently developed nonlinear control strategy for the position of the sheet is briefly reviewed. The core of this paper focuses on the addition of a nonlinear observer used to estimate the longitudinal, lateral, and angular positions of a sheet, by detecting its motion along two of its perpendicular sides. The success of the approach presented is corroborated through simulations, in which the estimates from the extended Luenberger observer designed are used on a nonlinear feedback control strategy.
2008 American Control Conference, 2008
Dual-stage servo systems have been proposed as a method for attaining increased bit densities fro... more Dual-stage servo systems have been proposed as a method for attaining increased bit densities from computer hard disk drives. To aid in controller operation, the second-stage microactuator used in a dual-stage system should operate at low voltages, feature relative position sensing, and have dynamics that interact well with the dynamics of the original drive servo. This paper describes a high-aspect ratio electrostatic microactuator modified to improve dynamic interactions, relative position sensor performance, and device yield. A multi-rate, multivariable control design technique was used to evaluate the closedloop performance of a disk drive system with a microactuator and relative position sensing. Closed-loop simulations reveal that the proposed configuration can reduce off-track position error. Addressing both hardware design and control design, this paper demonstrates the success of an integrated mechatronic approach to hard disk drive servo control.
6th IFAC Symposium on Mechatronic Systems, 2013, 2013
Volume 1: Active Control of Aerospace Structure; Motion Control; Aerospace Control; Assistive Robotic Systems; Bio-Inspired Systems; Biomedical/Bioengineering Applications; Building Energy Systems; Condition Based Monitoring; Control Design for Drilling Automation; Control of Ground Vehicles, Man..., 2014
In this paper we employ a modified filtered-x least mean squares (MFX-LMS) method to synthesis an... more In this paper we employ a modified filtered-x least mean squares (MFX-LMS) method to synthesis an adaptive repetitive controller for rejecting periodic disturbances at selective frequencies. We show how a MFX-LMS algorithm can be utilized when the reference signal is deterministic and periodic. A new adaptive step size is proposed with the motivation to improve the convergence rate of the MFX-LMS algorithm and fade the steady state excess error caused by the variation of estimated parameters in a stochastic environment. A novel secondary path modeling scheme is proposed to compensate for the modeling mismatches online. We further discuss the application of this adaptive controller in hard disk drives that use Bit Patterned Media Recording. Finally we present the results of comprehensive realistic numerical simulations and experimental implementations of the algorithms on a hard disk drive servo mechanism that is subjected to periodic disturbances known as repeatable runout.
2014 Conference on Information Storage and Processing Systems, 2014
2013 10th IEEE International Conference on Control and Automation (ICCA), 2013
Journal of Dynamic Systems, Measurement, and Control, 2006
In this paper we discuss the controller design of a PZT-actuated suspension dual-stage servo syst... more In this paper we discuss the controller design of a PZT-actuated suspension dual-stage servo system in hard disk drives. The proposed control structure includes an active vibration damping control loop and a track-following control loop. The vibration damping control loop, which runs at a faster rate than the track-following control loop, utilizes a PZT element on a PZT-actuated suspension as a vibration sensor to damp the resonance modes of the voice coil motor (VCM) and the PZT actuator. The vibration damping controller is designed using Kalman filter based state feedback control techniques. A simple dual-stage track-following controller is designed, based on the damped actuator model, using the sensitivity function decoupling design method. Simulation and experimental results are presented to demonstrate the benefits of this control scheme in expanding servo control bandwidth and suppressing airflow excited structural vibrations.