• 제어로봇시스템학회논문지
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• 제5권5호
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• pp.577-584
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• 1999

In this paper, the double inverted pendulum having a single actuator is built and the controller for the system is proposed. The lower link of the target pendulum system is hinged on the plate to free for rotation in the specified range($10^{\cire}$) on the x-z plane. The upper link is connected to the lower link through a DC motor. The double inverted pendulum built can be kept upright posture by controlling the position of the upper link even though it has no actuator in lower hinge. The algorithm to control the inverted pendulum consists of a state feedback controller within a linearizable range and a fuzzy logic controller coupled with a nonlinear feedback compensator for the rest of the range. Conventional state feedback control is employed, and the fuzzy controller is responsible for generating the reference joint angle of the upper link for the nonlinear feedback compensator which drives a DC motor to generate an indirect torque to the lower joint. As a result, we can get the upright posture of the proposed pendulum system. Simulations and experiments are conducted to show the validity of the proposed controller.

• 전력전자학회논문지
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• 제9권6호
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• pp.612-619
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• 2004

회전형 전동기와 볼스크류 및 타이밍 벨트를 이용한 서보 시스템은 NC, 가공기, 로봇 및 공장 자동화를 포함하여 산업 시스템 전반에 널리 사용되고 있다. 하지만, 동력의 전달에서 발생하는 비선형적인 마찰 및 댐핑현상은 제어 시스템 전체의 성능을 감소시키고, 특히 저속 정역 운전에서 그 영향이 크게 나타난다. 본 논문에서는 서보 제어시스템에서 발생하는 비선형적인 마찰 토크의 보상을 위해 가중치를 가지는 이중 제어 구조를 적용하였다. 본 논문에서 제안된 이중 제어 구조는 서보 제어 시스템에서 널리 사용되는 PI 속도 제어기 내부에 비선형적인 마찰 토크의 영향을 보상하는 내부 제어기를 가지는 구조이다. 특히, 내부의 제어기는 마찰 토크에 의한 시스템의 속도오차에 대하여 가중치를 가지는 구조로 설계되어 있고, 제어기의 이득은 외부 속도 제어기의 이득에 대하여 비례적으로 적용되므로, 안정성이 매우 높고 구조가 매우 간단하다. 본 논문에서 제안된 이중 제어 구조에 의한 비선형 마찰 토크 보상 방식은 시뮬레이션 및 실험을 통하여 그 성능을 검증한다.

• 전력전자학회논문지
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• 제18권4호
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• pp.322-332
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• 2013

Conventional single-phase series quasi Z-source voltage compensator can not compensate for voltage sag less than 50% that frequently occurs in the industrial field. In this study, single-phase series quasi Z-source voltage sag-swell compensator which can compensate the voltage variation of entire range is proposed. The proposed system is composed of two quasi Z-source AC-AC converters connected in series with output terminal stage. Voltage sag less than 50% could be compensated by the intersection switching control of the upper converter duty ratio and of the upper converter duty ratio. Also the compensation voltage and its flowchart for each compensation mode are presented for entire sag-swell region. To confirm the validity of the proposed system, a DSP(DSP28335) controlled experimental system was manufactured. As a result, the proposed system could compensate for the voltage sag/swell of 20% and 60%. Finally, voltage compensation factor and THD(Total Harmonic Distortion) according to voltage variation and load change were measured, and voltage quality shows a good results.

• 전력전자학회논문지
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• 제19권5호
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• pp.457-462
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• 2014

Given their low cost, single rolling piston compressors (SRPC) are utilized in low-power room air-conditioning systems. The SRPC cycle is composed of one compression and discharge process per mechanical rotation. The load torque is high during the compression process of the refrigerants and low during the discharge process of the refrigerants. This load torque variation induces a speed ripple and severe vibration, which cause fatigue failures in the pipes and compressor parts, particularly under low-speed conditions. To reduce the vibration, the compressor usually operates at a high-speed range, where the rotor and piston inertia reduce the vibration. At a low speed, a predefined feed-forward load torque compensator is used to minimize the speed ripple and vibration. However, given that the load torque varies with temperature, pressure, and speed, a predefined load torque table based on one operating condition is not appropriate. This study proposes an online load torque compensator for SRPC. The proposed method utilizes the speed ripple as a load torque ripple factor. The speed ripple is transformed into a frequency domain and compensates each frequency harmonic term in an independent feed-forward manner. Experimental results are presented to verify the proposed method.

• Journal of Power Electronics
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• 제19권4호
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• pp.869-880
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• 2019

Due to the inherent feedforward of load current, capacitor current (CC) control shows a fast transient response that makes it suitable for the power supplies used in various portable electronic devices. However, considering the effect of the outer voltage loop, the stable range of the duty-cycle is significantly diminished in CC controlled buck converters. To investigate the stability effect of the outer voltage loop on buck converters, a CC controlled buck converter with a proportion-integral (PI) compensator is taken as an example, and its second-order discrete-time model is established. Based on this model, the instability caused by the duty-cycle is discussed with consideration of the outer voltage loop. Then the dynamical effects of the feedback gain of the PI compensator and the equivalent series resistance (ESR) of the output capacitor on the CC controlled buck converter with a PI compensator are studied. Furthermore, the design-oriented closed-loop stability criterion is derived. Finally, PSIM simulations and experimental results are supplied to verify the theoretical analyses.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.580-585
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• 2005

A QRT(Quad-Rotor Type) hovering robot system is developed for quick detection and observation of the circumstances under calamity environment such as indoor fire spots. The UAV(Unmanned Aerial Vehicle) is equipped with four propellers driven by each electric motor, an embedded controller using a DSP, INS(Inertial Navigation System) using 3-axis rate gyros, a CCD camera with wireless communication transmitter for observation, and an ultrasonic range sensor for height control. The developed hovering robot shows stable flying performances under the adoption of RIC(Robust Internal-loop Compensator) based disturbance compensation and the vision based localization method. The UAV can also avoid obstacles using eight IR and four ultrasonic range sensors. The VTOL(Vertical Take-Off and Landing) flying object flies into indoor fire spots and sends the images captured by the CCD camera to the operator. This kind of small-sized UAV can be widely used in various calamity observation fields without danger of human beings under harmful environment.

• 한국정밀공학회지
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• 제29권1호
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• pp.79-86
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• 2012

This paper proposes PID and RIC (Robust Internal-loop Compensator) based motion controller using dual learning algorithm for position control of linear synchronous motor respectively. Its gains are auto-tuned by using two learning algorithms, reinforcement learning and neural network. The feedback controller gains are tuned by reinforcement learning, and then the feedforward controller gains are tuned by neural network. Experiments prove the validity of dual learning algorithm. The RIC controller has better performance than does the PID-feedforward controller in reducing tracking error and disturbance rejection. Neural network shows its ability to decrease tracking error and to reject disturbance in the stop range of the target position and home.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.399-402
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• 1996

The electrodynamic loudspeakers should have a wide dynamic range to reproduce various sound levels. When the input signal is small, the radiated sound from the loudspeaker is not so much distorted. However, for large input signal with low frequency component the radiated sound is significantly distorted due to the nonlinearities of the loudspeaker. The suspension, damping, and magnetic flux of loudspeaker are the main sources of the nonlinearity. Such electromechanical parameters related to harmonic distortion have been represented by a polynomial model for diaphragm displacement, while each of the polynomial coefficient is evaluated by using the principle of harmonic balance experimentally. Based on the polynomial model, we designed a compensator for nonlinear harmonic distortion of direct radiator loudspeaker. Than observer is used to estimate the displacement of the loudspeaker diaphragm, which is rather difficult to measure directly in the conventional setting. The usefulness of the designed compensator is demonstrated by numerical simulations. Simulation results show about 30db decrease at the second and third higher harmonic distortions. We carry out an experiment on speaker to verify designed controller and nonlinear observer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 C
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• pp.1035-1038
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• 1999

To improve the damping of all poorly damped oscillation modes, a control strategy of Static Synchronous Series Compensator (SSSC) based on energy method is presented in this Paper As a synchronous voltage-sourced inverter, SSSC is used to provide controllable series compensation. SSSC can provide controllable compensating voltage over an identical capacitive and inductive range. The damping effect of control strategy based on energy function is robustness with respect to loading condition, fault location and network configuration. Furthermore, the control inputs are based on local signals. In two area system, the effect of damping inter-area mode oscillation is demonstrated by the robust control strategy of SSSC.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.593-594
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• 2008

In this article, process voltage temperature (PVT) compensated on-chip oscillator is implemented by using proportional to absolute temperature (PTAT) circuit and process compensator. Process compensator circuit based on current subtracter and PTAT circuit are proposed for compensation of oscillation frequency to cope with process variation and temperature variation. All circuit can operate in the range of $3.5{\sim}5\;V$ supply voltage. It can be applied to PVT insensitive low frequency clock reference generator.