• International Journal of Control, Automation, and Systems
• /
• v.5 no.3
• /
• pp.243-250
• /
• 2007

This paper presents a systematic method of estimating a velocity disturbance occurring in the fine seek control system of an optical disk drive. A fine seek loop gain adjustment algorithm is introduced to accurately estimate the velocity disturbance in spite of the uncertainties of the fine actuator. The velocity disturbance can be estimated from a measurable velocity, a fine seek controller output, and a compensated fine actuator model. A robust fine seek controller can be designed by considering a minimum fine seek open-loop gain, calculated by the estimated velocity disturbance. The proposed controller design method is applied to the fine seek control system of a DVD rewritable drive and is evaluated through the experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.50 no.8
• /
• pp.541-550
• /
• 2022

An effective real time fault diagnosis approach for UAV engine is drawn from IMM filter and GLRT methods. For this purpose based on the linear diagnosis model derived from engine dynamic performance analysis the Kalman filter for residual estimation and each method are applied to the fault diagosis of the actuator for engine control sensors. From the process of the IMM filter application the effective FDI measure is obtained and the state responses due to actuator fault are estimated. Likewise from the GLRT method the fault magnitudes of actuator and sensors are estimated associated with some FDI functionings. The numerical simulations verify the effectiveness of the IMM filter for FDI and the GLRT in estimating the fault magnitudes of each fault mode.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.298-302
• /
• 2002

Equivalent volume estimation of the coupler and two coupled microphones has a key role in standard microphone pressure calibration. The equivalent volume of the microphone is determined by the dynamic characteristics of the diaphragm system and front cavity. Therefore the modal parameters of diaphragm system - natural frequency and damping fatter - should be measured explicitly for the estimation of the equivalent volume. The diaphragm system is composed of the vibrating diaphragm, back slit behind diaphragm, pressure equalization vent, and front cavity which are acoustically coupled. In the measurement, the electrostatic actuator was used to excite the system with the swept sine, and the frequency response was obtained. The close actuator in front of the diaphragm must influence the radiation impedance of the system, and then the modal parameters. From the measured frequency response, the natural frequency and the damping factor could be estimated with the Complex exponential method based on the Prony model and the zero crossing real and imaginary plot.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.54.4-54
• /
• 2001

This paper proposes an adaptive control scheme for an autopilot design of Relaxed-Static-Stability(RSS) Missiles with saturating actuator. The feedback linearization controller eliminates nonlinear terms in RSS missile dynamics and makes the entire system linear. But modeling errors, disturbances and the nonlinear mismatch due to input constraints exert a bad influence on the performance of the feedback linearization controller Thus, first, we derive a parametric affine uncertainty model with modeling errors and disturbances. Then an adaptive control law with anti-windup scheme is developed, where the bounds of uncertainties are estimated with adaptive laws. The proposed adaptive controller can remove the bad effects of uncertainties, of disturbances, and of saturating actuator ...

• Smart Structures and Systems
• /
• v.24 no.3
• /
• pp.361-377
• /
• 2019

The stiffness of shape memory alloy (SMA) spring while in actuation is represented by an empirical model that is derived from the logistic differential equation. This model correlates the stiffness to the alloy temperature and the functionality of SMA spring as active variable stiffness actuator (VSA) is analyzed based on factors that are the input conditions (activation current, duty cycle and excitation frequency) and operating conditions (pre-stress and mechanical connection). The model parameters are estimated by adopting the nonlinear least square method, henceforth, the model is validated experimentally. The average correlation factor of 0.95 between the model response and experimental results validates the proposed model. In furtherance, the justification is augmented from the comparison with existing stiffness models (logistic curve model and polynomial model). The important distinction from several observations regarding the comparison of the model prediction with the experimental states that it is more superior, flexible and adaptable than the existing. The nature of stiffness variation in the SMA spring is assessed also from the Dynamic Mechanical Thermal Analysis (DMTA), which as well proves the proposal. This model advances the ability to use SMA integrated mechanism for enhanced variable stiffness actuation. The investigation proves that the stiffness of SMA spring may be altered under controlled conditions.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.3
• /
• pp.452-460
• /
• 2002

The precision stage using a novel contact-free planar actuator based on magnetic farces, magnetized force and Lorentz farce, is suggested. In the promising magnetic structure, the mover is driven directly without any transmission mechanism, and doesn't need any auxiliary driver for its posture calibration. Then it is estimated that the proposed operating principle is very suitable for work requiring high accuracy and cleanness, or general-purpose nano-stage. In this paper, we discuss a driving principle of the planar system including the magnetic force generation mechanism, a framework for the force model, governing characteristics of the levitated plate, and a planar motion control of the constructed prototype. And experimental results are given to verify the derived theoretical model and a feasibility of the system.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.7
• /
• pp.72-78
• /
• 2008

The line-of-sight(LOS) stabilization system is a precision electro-mechanical gimbals assembly for suppressing vibration due to its environment and tracking the target in a desired direction. This paper describes the design of gimbals system to reject the disturbance and to improve stabilization. The controller consists of a DSP with transducer and actuator interfaces. Unknown parameters of the gimbals are estimated by the signal compression method. The cross-correlation coefficient between the impulse response from the assumed model and the one from model of the gimbals is used to obtain the better estimation. The quasi-impulse response through linear element included in the gimbals could be obtained by the signal compression method. The unknown parameter of the linear element could be estimated as comparing the bode plots for impulse response from gimbals with them from model's response.

• Journal of the Semiconductor & Display Technology
• /
• v.11 no.3
• /
• pp.13-18
• /
• 2012

This paper presents a velocity disturbance estimation system for the stable fine seek control using a genetic algorithm. To estimate accurately the velocity disturbance in spite of the uncertainties of fine actuator, the system utilizes an objective function to minimize the differences of the frequency characteristics between the nominal velocity control loop and the extremal velocity control loops. The objective function is considered by applying a genetic algorithm and the velocity disturbance is estimated by the measurable velocity, the adjusted velocity controller, and the fine actuator model. The proposed velocity disturbance estimation system is applied to the fine seek control system of a DVD recording device and is evaluated through the experimental results.

• Smart Structures and Systems
• /
• v.6 no.1
• /
• pp.29-38
• /
• 2010

An ElectroMagnetic Actuator (EMA) is designed and assessed numerically and experimentally. The EMA has the advantage to be without contact with the structure so it could be applied to light and small mechanism. Nevertheless, the open-loop instability and the nonlinear dynamic behavior with respect to the excitation frequency could limit its application field. The EMA is designed and dimensioned as a function of the experimental structure to be controlled. An inverse model of the EMA is proposed in order to implement a linear action block for the used frequency range. The control strategy is a fuzzy controller with displacements and velocities as inputs. A fuzzy controller of Takagi-Sugeno type is used. The air gap is estimated by using a modal approximation of the displacements issued from all measurements. Several configurations of control are assessed by using numerical simulations. The block diagram used for numerical simulations is implemented under Dspace$^{(R)}$ environment. The implemented controller was tested experimentally in the context of impact perturbations. The results obtained show the effectiveness of the developed procedures and the robustness of the implemented control.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.892-895
• /
• 1996

An unknown input observer is proposed that can be used in wheelbase preview control of commercial vehicles. The preview and state information, required to calculate actuator force, are reconstructed from the measurement variables such as heave and pitch acceleration. Gain matrix of observer is optimally selected so that influence of system and measurement noises on the estimation error can be minimized. Estimated preview information requires low pass filtering to eliminate high frequency components resulting from differentiation of noisy output signals. Effectiveness of the proposed method is demonstrated by numerical simulation of half car model.