• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.225-231
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• 2000

Nonlinear characteristics of piezoelectric-type micro actuator used for hard disk drives are experimentally analyzed using Hutchinson's Magnum acturator. The nonlinear effects include hysteresis, superharmonic resonance, jump phenomenon, and shifting of natural frequencies. The effects of exciting frequency and input voltage on the nonlinear phenomena are investigated. It is shown that the micro actuator has the typical 3 times superhamonic resonances coupled to both 1st torsional and sway modes of the suspension.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1990-1996
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• 2004

This paper presents a nonlinearly modulated digital actuator (NMDA) for producing nano-precision digital stroke. The NMDA, composed of a digital microactuator and a nonlinear micromechanical modulator, purifies the stroke of the digital actuator in order to generate the high-precision displacement output required for nano-positioning devices. The function and concept of the nonlinear micromechanical modulator are equivalent to those of the nonlinear electrical limiters. The linear and nonlinear modulators, having an identical input and output strokes of 15.2${\mu}{\textrm}{m}$ and 5.4${\mu}{\textrm}{m}$, are designed, fabricated and tested, respectively. The linear and nonlinear modulators are linked to identical digital actuators in order to compare the characteristics of the linearly modulated microactuator (LMDA) and NMDA. In addition, an identical linear modulator is attached to the output ports of LMDA and NMDA. The NMDA shows the repeatability of 12.3$\pm$2.9nm, superior to that of 27.8$\pm$2.9nm achieved by LMDA. When the identical linear modulator is connected to LMDA and NMDA, the final modulated output from NMDA shows the repeatability of 10.3$\pm$7.2nm, superior to that of 15.7$\pm$7.7nm from LMDA. We experimentally verify the displacement purifying capability of the nonlinear mechanical modulator, applicable to nano-precision positioning devices and systems.

• Journal of Applied Reliability
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• v.12 no.3
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• pp.215-224
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• 2012

This paper deals with a design of fault tolerant state feedback controllers for continuous time nonlinear time delay systems with actuator failures. The goal is to find an asymptotically stabilizing controller such that the closed loop system achieves the prescribed $H_{\infty}$ performance objective in the actuator fault cases. Based on a sum of squares (SOS) approach, a design method for $H_{\infty}$ fault tolerant controller is presented. In order to demonstrate our design method, a numerical example is provided.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2002-2008
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• 2001

Nonlinear vibration characteristics of a piezoelectric-type micro actuator used for hard disk drives are experimentally studied. The nonlinear characterisitics include hysteresis, superharmonic resonance, jump phenomenon, and shifting of natural frequencies. The vibration modes and frequencies of the commercial actuator of the Hutchinson's Magnum series are measured using a laser vibrometer. From harmonic excitation to the PZT acturator, we observe interesting hysteresis patterns with 3 times input frequency. It is shown that the micro actuator has the typical 3 times superhamonic resonances coupled to the first torsional and sway modes of the suspension.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.139-142
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• 1997

In this paper, a robust controller is proposed to achieve an accurate tracking for an uncertain nonlinear plant with actuator dynamics. The extent of parameter uncertainty can be quantified by using linear parameterization technique. A switching controller is proposed to guarantee the global asymptotic stability of the plant. In order to eliminate the chattering caused by the switching controller, a smoothing controller is designed using the boundary layer technique around the sliding surface and guarantees the uniform ultimate boundedness of the tracking error.

• Journal of Aerospace System Engineering
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• v.9 no.4
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• pp.23-30
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• 2015

The focal plane image stabilization for a camera is one of the most effective method that can increases the digital camera's image quality by compensating the vibration disturbance. The optical image stabilization can be implemented by making the focal plane to trace the path of incident light. To control the position of focal plane motion compensating stage precisely, a nonlinear control algorithm has been applied by considering coulomb friction which is nonlinear behavior of the compensator system. In our study, we have analyzed the hand shaking vibration using the gyro sensor, and made a mathematical model of compensating stage containing optical sensor and piezo-actuator. Then the nonlinear control algorithm has been designed and its performance has been verified by experiment. In this study, a friction driven peizo-electric actuator with $1{\mu}m$ resolution and 10mm/s speed has been used for stage movement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1423-1428
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• 2011

This paper proposes a learning input shaper with nonlinear actuator dynamics to reduce the residual vibration of flexible systems. The controller is composed of an estimator of the time constant of the nonlinear actuator dynamics, a recursive least squares method, and an iterative updating algorithm. The updating mechanism is modified by introducing a vibration measurement function to cope with the dynamics of nonlinear actuators. The controller is numerically evaluated with respect to parameter convergence and control performance by using a benchmark pendulum system. The feasibility and applicability of the controller are demonstrated by comparing its control performance to that of an existing controller algorithm.

• Smart Structures and Systems
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• v.9 no.2
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• pp.127-143
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• 2012

The present paper deals with the nonlinear analysis of the functionally graded piezoelectric (FGP) annular plate with two smart layers as sensor and actuator. The normal pressure is applied on the plate. The geometric nonlinearity is considered in the strain-displacement equations based on Von-Karman assumption. The problem is symmetric due to symmetric loading, boundary conditions and material properties. The radial and transverse displacements are supposed as two dominant components of displacement. The constitutive equations are derived for two sections of the plate, individually. Total energy of the system is evaluated for elastic solid and piezoelectric sections in terms of two components of displacement and electric potential. The response of the system can be obtained using minimization of the energy of system with respect to amplitude of displacements and electric potential. The distribution of all material properties is considered as power function along the thickness direction. Displacement-load and electric potential-load curves verify the nonlinearity nature of the problem. The response of the linear analysis is investigated and compared with those results obtained using the nonlinear analysis. This comparison justifies the necessity of a nonlinear analysis. The distribution of the displacements and electric potential in terms of non homogenous index indicates that these curves converge for small value of piezoelectric thickness with respect to elastic solid thickness.

• Journal of Applied Reliability
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• v.12 no.2
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• pp.121-129
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• 2012

This paper deals with a design of reliable state feedback controllers for continuous time polynomial systems with actuator failures. The goal is to find an asymptotically stabilizing controller such that the closed loop system achieves the prescribed decay rate in the actuator failure cases. Based on a sum of squares (SOS) approach, a design method for reliable nonlinear controller is presented. In order to demonstrate our design method, a numerical example is shown.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.259-262
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• 2003

This paper is proposed a new linear actuator with the permanent magnet on the mover. This linear actuator is designed to produce the vibration of a osillator. In order to evaluate its dynamic performance, the equivalent coupling parameter between mechanical and electromagnetic equations of the linear actustor, which is considered the magnetic nonlinear phenomena, is analyzed by the finite element method and estimated the thrust, displacement and acceleration with the simualation values and the experimenta ones.