• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.280-286
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• 1998

This paper proposes a novel method to reduce the torque ripple due to the non-ideality of the current sensing parts in vector-controlled inverter-fed AC motor drive systems. For PMSM(Permanent Magnet Synchronous Motor), motor output torque equations are derived in terms of their offset voltages and different voltage transducing gains. And the effects of phase current errors on motor torque are analyzed for both salient PMSM and non-salient PMSM. The proposed method can eliminate the torque ripple by nulling the offset voltages and setting the voltage transducing gains to the same value. To verify the proposed method, digital simulations are carried out for non-salient PMSM.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.7 no.2
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• pp.7-12
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• 2013

In this paper, we propose a brushless DC motor drive system for active knee prosthesis and low-cost estimation method for phase current from DC-link current. To control motor torque directly, current sensing is very important and current sensing point should be synchronized with voltage switching command to minimize the effect of switching noise in current measurement, For maintaining small form factor, simplifying control schemes and achieving low-cost system, control schemes using DC-link current are used. Moreover, we incorporated phase current estimation method using analog MUX for minimizing current estimation error between DC-link current and phase current. The validity of the proposed system is verified through experimental works.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.590-593
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• 2004

Extraction of ocean surface current velocity offers important physical oceanographic parameters especially on understanding ocean environment. Although Remote Sensing techniques were highly developed, the investigation of ocean surface current using Synthetic Aperture Radar (SAR) is not an easy task. This paper presents the results of ocean surface current observation using Doppler Centroid of ERS-1 SAR data obtained off the coast of Korea peninsula. We employed the concept, in which Doppler frequency shift and the ocean surface current are closely related, to evaluate ocean surface current. Moving targets cause Doppler frequency shift of the back scattered radar waves of SAR, thus the line-of-sight velocity component of the scatters can be evaluated. The Doppler frequency shift can be measured by estimating the difference between Doppler Centroid of raw SAR data and reference Doppler Centroid. Theoretically, the Doppler Centroid is zero; however, squinted antenna which is affected by several physical factors causes Doppler Centroid to be nonzero. The reference Doppler Centroid can be obtained from measurements of sensor trajectory, attitude and Earth model. The estimated Doppler Centroid was compensated by considering the accurate attitude estimation of ERS-1 SAR. We could verify the correspondence between the estimated ocean surface current and observed in-situ data in the error bound.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.151-159
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• 2007

This paper proposes a improved decoupling current control algorithms using a compensator to enhance the robustness to the stator inductance error. And the compensator composed from a d-axis current error for sensing change of the real stator inductance can match the estated stator inductance to the real stator inductance. A great advantage of this algorithms is more robust than feedforward decoupling current control or dynamic decoupling control. So it looks suitable to the practical applications where the exact parameters are unknown. Though simulation and experimental results with 1[kW] prototype PMSM and TMS320F2812 board for motor control, we show that the proposed controller achieves the desired performance.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.187-190
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• 2007

The Geostationary Ocean Color Imager (GOCI) is under development to provide a monitoring of ocean-color around the Korean Peninsula from geostationary platforms. It is planned to be loaded on Communication, Ocean, and Meteorological Satellite (COMS) of Korea. The GOCI has been designed to provide multi-spectral data to detect, monitor, quantify, and predict short term changes of coastal ocean environment for marine science research and application purpose. The target area of GOCI observation covers sea area around the Korean Peninsula. Based on the nonlinear radiometric model, the GOCI calibration method has been derived. The nonlinear radiometric model for GOCI will be validated through ground test. The GOCI radiometric calibration is based on on-board calibration devices; solar diffuser, DAMD (Diffuser Aging Monitoring Device). In this paper, the GOCI radiometric error propagation is analyzed. The radiometric model error due to the dark current nonlinearity is analyzed as a systematic error. Also the offset correction error due to gain/offset instability is considered. The radiometric accuracy depends mainly on the ground characterization accuracies of solar diffuser and DAMD.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.356-361
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• 2005

In this paper, a new scheme of current programmed control for three phase PWM AC-AC converter is presented. Compared to duty-ratio voltage control, current programmed control has several advantages such as reduction of system order and inherent current protection. By considering only the magnitude components, the same scheme in the DC-DC converter can be extended to the three phase PWM AC-AC converter. Sensing the output voltage and the inductor current, an error signal will be generated by comparing the output voltage magnitude with a reference value. Then the error signal will be processed by a PI compensator to generate the current command. The converter switches will the change the state by a periodic clock pulse or at the instants when the inductor current magnitude reaches the current command. As an example case, the buck converter is treated. The converter analysis is carried out by applying the complex DQ circuit transformation to obtain basic physical insight into the converter operation and to establish some important characteristic equations for control purpose. The simulation with Simplorer shows the validity of the proposed scheme and the experimental results support the verification of the design.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.12
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• pp.993-998
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• 2017

In this paper, a high-accuracy current sensing technique for three-phase current paths in an electrical switchboard is proposed. Conventional open-style current sensors using magnetic sensors show inaccurate sensing performance with more than 10% error due to undesired magnetic field interference from neighboring paths. To increase accuracy, large and expensive current transformers with large permeabilities have been used, which increased the cost and size. The proposed technique can improve the measured magnetic field by the calculation of magnetic interference effect from neighboring current paths. The relationship between neighboring magnetic fields and the desired magnetic field is theoretically analyzed in a general case. The proposed technique is verified using magnetic field simulations in a three-phase busbar environment.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.339-341
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• 2006

This paper presents a new method on controller design of brushless dc motors. In such drives the current ripples are generated by motor inductance in stator windings and the back EMF. To suppress the current ripples the current controller is generally used. To minimize the size and the cost of the drives it is desirable to control motors without the current controller and the current sensing circuits. To estimate the motor current it is modeled by a neural network that is configured as an output-error dynamic system. The identified model is essentially a one step ahead prediction structure in which fast inputs and outputs are used to calculate the current output. Using the model, effective estimator to compensate the effects of disturbance has been designed. The effectiveness of the proposed current estimator is verified through experiments.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.6
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• pp.589-595
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• 2007

This paper presents a new method on controller design of brushless dc motors. In such drives the current ripples are generated by motor inductance in stator windings and the back EMF. To suppress the current ripples the current controller is generally used. To minimize the size and the cost of the drives it is desirable to control motors without the current controller and the current sensing circuits. To estimate the motor CUlTent it is modeled by a neural network that is contigured as an output-error dynamic system. The identified model is essentially a one step ahead prediction structure in which past inputs and outputs are used to calculate the current output. Using the model, a state feedback controller to compensate the effects of disturbance has been designed. The controller is implemented by a 16-bit microprocessor and the effectiveness of the proposed control method is verified through experiments.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.230-230
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• 2000

This paper describes a model reference adaptive system(MRAS) for speed control of vector-controlled induction motor without a speed sensor. The proposed approach is based on observing the instantaneous torque. The real torque is calculated by sensing stator current and estimated torque is calculated by stator current that is calculated by using estimated rotor speed. The speed estimation error is linearly proportional to error between real torque and estimated torque. The proposed feedback loop has linear component. Furthermore proposed method is robust to parameters variation. The effectiveness is verified by equation and simulation