• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.5
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• pp.421-427
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• 2005

A closed-loop sensorless stroke control system for a linear compressor has been designed. The motor parameters are identified as a function of the piston position and the motor current. They are stored in ROM table and used later for the accurate estimation of piston position. Also it was attempted to approximate the identified motor parameters to the 2nd-order surface functions. Some experimental results are given in order to show the feasibility of the proposed control schemes for linear compressors.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.3
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• pp.232-238
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• 2015

A sensorless control algorithm of brushless DC (BLDC) motors with a model current based on 120 degree conduction mode is proposed in this paper. The rotor speed and position can be estimated using the current model of BLDC motor, which is a modified version of the conventional current model of permanent magnet synchronous motor. The rotor speed and position can be obtained using the difference of the actual current and the model current. The position error caused by the parameter errors of the model current is compensated using a PI controller and the feedback loop of the real current. The validity of the proposed sensorless control algorithm is verified through simulation.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.607-612
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• 1992

This paper presents a tip position control of a single-link flexible arm with a payload by using closed loop control. The shifting problem of the arm from the initial position to desired position is considered by the variation of the displacement gain $G_{p}$ and velocity gain $G_{v}$. The system is composed of a flexible arm with payload, DC servomotor, and a ballscrew mechanism. The flexible arm is mounted on a mobile stage driven by a servomotor and ballscrew. As a result, the increase of the displacement and velocity gain respectively comes to the reduction of tip vibration. Theoretical results are approximately in good agreement with those obtained experimentally.y.y.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1166-1176
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• 2017

Estimation errors of the rotor speed and position in sensorless control systems of Permanent Magnet Synchronous Motors (PMSM) will lead to low efficiency and dynamic-performance degradation. In this paper, a parallel-type extended nonlinear observer incorporating the nominal parameters is constructed in the stator-fixed reference frame, with rotor position, speed, and the load torque simultaneously estimated. The stability of the extended nonlinear observer is analyzed using the indirect Lyapunov's method, and observer gains are selected according to the transfer functions of the speed and position estimators. Taking into account the parameter inaccuracies issue, explicit estimation error equations are derived based on the error dynamics of the closed-loop sensorless control system. An equivalent flux error is defined to represent the back Electromotive Force (EMF) error caused by the inaccurate motor parameters, and a compensation strategy is designed to suppress the estimation errors. The effectiveness of the proposed method has been validated through simulation and experimental results.

• Journal of Power System Engineering
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• v.17 no.3
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• pp.82-88
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• 2013

For commercialized servo drives of the motion stage to include embedded controller, external terminal is provided for tracking command and encoder output, but internal terminal is not for control input. Thus, it is difficult to combine out signal of embedded controller with that of external compensator such as disturbance observer. In this study, for precise tracking control of motion stage without hardware change of the servo drive, tacking control system is composed of an inner loop of servo drive and an outer loop of disturbance observer. Then, the control system is designed so that the output response of actual plant corresponds with nominal model's in transient state as well as in steady state. Finally, the experiment results show that the designed control system is effective to reconcile actual plant behavior with nominal model under nonlinear friction and parameter perturbation.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.3
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• pp.1-12
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• 2003

The complexity of the papermaking system accelerates interactions between a large number of variables involved. The process operation, therefore, is subject to frequent perturbations by disturbance. Dynamic modelling is a useful tool for characterizing the transient behavior and selecting the best control strategies to reject disturbances. In this study we developed a dynamic simulation model of a fine paper production process, which consists of stock preparation, wire sections, white water circulations, and broke system. It focused on dynamic simulation in its role for developing control strategies and studying control loop dynamics related to filler loading for ash control. The results emphasized the importance of filler-loading position and length of control loop for rapid ash control and process stabilization.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.157-163
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• 2014

In this paper, a robust MRAC (model reference adaptive control) scheme is applied to control an electrohydraulic positioning system under various loads. The inverse dead-zone compensator in the control system cancels out the dead-zone response, and an integrator added to the controller provides good position-tracking ability. LQG/LTR (linear quadratic Gaussian control with loop transfer recovery) closed-loop model is used as the reference model for learning the MRAC system. LQG/LTR provides a systematic technique to design the linear controller that optimizes the objective function using some compromise between the control effort and the system performance in the frequency domain. Different external load tests are performed to investigate the effectiveness of the designed MRAC system in real time. The experimental results show that the tracking performance of the proposed system is highly accurate, which offers considerable robustness even with a large change in the load.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.7
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• pp.502-507
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• 2016

In this paper, we propose a tracking control method for a quadrotor equipped with a 2-DOF manipulator, which is based on the multiple sliding surface control (MSSC) method. To derive the model of a quadrotor equipped with a 2-DOF manipulator, we obtain the models of a quadrotor and a 2-DOF manipulator based on the Lagrange-Euler formulation separately - and include the inertia and the reactive torque generated by a manipulator when these obtained models are combined. To make a quadrotor equipped with a manipulator track the desired path, we design a double-loop controller. The desired position is converted into the desired angular position in the outer controller and the system's angle tracks the desired angular position through the inner controller based on the MSSC method. We prove that the position-tracking error asymptotically converges to zero based on the Lyapunov stability theory. Finally, we demonstrate the effectiveness of the proposed control system through a computer simulation.

• Proceedings of the IEEK Conference
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• 2000.06e
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• pp.39-42
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• 2000

In this paper we design the robust impedance controller of the robot manipulator with time delay. The designed controller considers time delay in the position loop and stabilizes the closed-loop system. The performance of a controller can be easily degraded by external disturbances. To improve the performance when external disturbances exist, we use the disturbance observer to handle the disturbances in the velocity loop and provide robustness to the control system. To show the validity of the designed controller, several experiments are performed for the 5-DOF robot manipulator equipped with the wrist force/torque sensor system.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.604-607
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• 2000

In this paper we design the robust impedance controller of the robot manipulator with time delay. The designed controller considers time delay in the position loop and stabilizes the closed-loop system. The performance of a controller can be easily degraded by external disturbances. To improve the performance when external disturbances exist, we use the disturbance observer to handle the disturbances in the velocity loop and provide robustness to the control system. To show the validity of the designed controller, several experiments are performed for the 5-DOF robot manipulator equipped with the wrist force/torque sensor system.