• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.120-121
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• 2017

This paper proposes an enhanced distributed generation (DG) unit with an adaptive virtual impedance control approach in order to address the inaccurate reactive power sharing problem. The proposed method can adaptively regulate the DG virtual impedance, and the effect of the mismatch in feeder impedances is compensated to share the reactive power accurately. The proposed control strategy is fully distributed and the need for the microgrid central controller is eliminated. Furthermore, the proposed method can be directly implemented without requirement of pre-knowledge of the feeder impedances. Simulations are performed to validate the effectiveness of the proposed control approach.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.5
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• pp.259-267
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• 2019

This paper proposes a structure of a variable impedance control system based on sensor-less external force estimator of industrial manipulators for cyber physical production systems (CPPS). To implement CPPS, a feedback system is constructed by using the robot operating system (ROS) and an external force estimator which is designed to measure the external force applied to the manipulator without a force sensor. Based on the robot dynamics, the robot-human cooperating system for the cyber physics production system is implemented through a controller that changes the impedance characteristics of the manipulator according to the situation using the external force estimator. Simulation and experimental results verify the effectiveness of the proposed control system.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1487-1490
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• 2005

This study proposes a controller with the techniqu e of voltage -compensated driver for producing grayscaled pictures on passive matrix organic light emitting diodes (PMOLEDs) panels; especially, the controller overcomes the problem of luminance nonuniformity on displaying pictures. Because the controller is a voltage type driver, the output impedance of the driver is much less than that of the current-type driver. Hence, the controller provides a better electron-optical response than those of traditional current drivers. An area compensated look-up table (ACLUT) is designed in data feeding paths for removing luminance non-uniformity; thus, the proposed controller provides nearly 95% luminance uniformity.

• Journal of Power Electronics
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• v.15 no.3
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• pp.577-586
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• 2015

The combination of voltage feedforward and feedback control is a conventional approach for correcting the power factor in single-phase ac-dc boost converters. The feedback duty ratio increases significantly with an increase of the line frequency and input inductance. Therefore, the performance of the conventional approach is highly dependent on the bandwidth of the feedback controller. As a result, the input power quality can be significantly exacerbated due to uncompensated duty ratios if the feedback controller is limited. This paper proposes an input impedance and current feedforward control method to reduce the control portion of the feedback controller. The findings in this paper are 1) the theoretical derivation and analysis of variations of line frequency and input inductance on a power factor correction approach, 2) guaranteed consistent performance in a wide range of conditions, and 3) that a low switching frequency can be utilized by the proposed method. A MATLAB/Simulink model and a 1.2kW dual boost converter are built to demonstrate the effectiveness of the proposed method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.81-82
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• 2013

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1078-1081
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• 2004

A robot manipulator is usually operated in two modes: free motion and constraint motion depending on whether the robot comes into contact with the environment or not. At the moment of contact, impact occurs, and sometimes, it possibly degrade the robot's performance by vibration and at worst, shortens its lifetime. In this article, a new proposed algorithm is described by introducing a command signal modification method on the basis of impedance control and a validity of the proposed algorithm is demonstrated by showing a simulation and an experiment.

• Journal of IKEEE
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• v.26 no.4
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• pp.659-670
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• 2022

An 830-Mb/s/pin transceiver for a controller supporting ×32 LPDDR2 memory is designed. The transmitter consists of eight unit circuits has an impedance in the range of 34Ω ∽ 240Ω, and its impedance is controlled by an impedance correction circuit. The transmitted DQS signal has a phase shifted by 90° compared to the DQ signals. In the receive operation, the read time calibration is performed by per-pin skew calibration and clock-domain crossing within a byte. The implemented transceiver for the LPDDR2 memory controller is designed by using a 55-nm process using a 1.2V supply voltage and has a maximum signal transmission rate of 830 Mb/s/pin. The area and power consumption of each lane are 0.664 mm² and 22.3 mW, respectively.

• The Journal of Korea Robotics Society
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• v.13 no.3
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• pp.157-163
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• 2018

This paper deals with the development and application of control algorithms for series elastic relief robots for rescue operations in harsh environment like disasters or battlefield. The joint controller applied in this paper has a cascade structure combining inner loop for torque control and outer loop for position control. The torque loop contains feedforward and feedback controller and disturbance observer for independent, decentralized joint control. The effect of the elastic component and motor dynamics are treated as the nonlinear disturbance and compensated with the disturbance observer of torque controller. For the collision detection, Band Designed Disturbance Observer is configured to recognize/respond to external disturbance robustly in the continuously changing environment. The controller is applied to a 7-dof series elastic manipulator to evaluate the torque tracking and collision detection/response performance.

• Journal of Power Electronics
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• v.13 no.3
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• pp.409-418
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• 2013

This paper presents an enhanced control strategy which consists of a proportional-integral controller and a repetitive controller (RC) for improving the voltage performance of distributed generation (DG) under nonlinear load conditions. The proposed voltage controller is able to maintain a sinusoidal voltage at the point of common coupling (PCC) of the DG regardless of the harmonic voltage drop in the system impedance due to nonlinear load currents. In addition, by employing the delay time of the RC at one-sixth of the fundamental period, the proposed RC can overcome the slow response drawback of the traditional PI-RC. The proposed control strategy is analyzed and the design of the RC is presented in detail. The feasibility of the proposed control strategy is verified through simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.256-257
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• 2012

This paper presents a new control strategy to improve voltage performance of distributed generation (DG) under nonlinear loads. The proposed voltage controller consists of a proportional-integral and a repetitive controller where the repetitive controller behaves as a bank of resonant controllers to compensate harmonic voltage drop on system impedance due to nonlinear load current. As a result, the voltage at the point of common coupling (PCC) of the DG is regulated to be sinusoidal waveform regardless of the presence of nonlinear loads. In order to validate the effectiveness of the proposed voltage controller, simulations are carried out using PSIM software and results are compared with those with the conventional PI controller.