• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권2호
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• pp.107-115
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• 2006

In this paper, a new speed sensorless control based on an instantaneous reactive power is proposed for the interior permanent magnet synchronous motor(IPMSM) drives. In proposed algorithm, the current observer estimates the line currents and the estimated speed can be yielded from the voltage equation because the information of speed is included in back EMF. To implement speed sensorless control, the current observer is composed by using the voltage equation of the IPMSM in the stationary reference frame fixed to the stator. The estimated speed of the rotor is composed by using the voltage equation of the IPMSM in the rotating reference frame fixed to the rotor The estimated speeds to minimize the speed error compensated by using the instantaneous reactive power. The instantaneous reactive power is calculated on the rotating reference frame fixed to the rotor. The effectiveness of the preposed algorithm is confirmed by the experiments.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.630-637
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• 2003

This paper proposes a new modeling scheme to describe the hysteresis and the dynamic characteristics of piezoelectric actuators in the inchworm and develops a control algorithm for the precision motion control. From the analysis of piezoelectric actuator behaviors, the hysteresis can be described by the functions of a maximum input voltage. The dynamic characteristics are also identified by the frequency domain modeling technique based on the experimental data. For the motion control, the hysteresis behavior is compensated by the inverse hysteresis model. The dynamic stiffness of an inchworm is generally low compared to its driving condition, so mechanical vibration may degenerate the motion accuracy of the inchworm. Therefore, the sliding mode control and the Kalman filter are developed for the precision motion control of the inch-warm. To demonstrate the effectiveness of the proposed modeling schemes and control algorithm, experiment validations are performed.

• 한국산업융합학회 논문집
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• 제18권1호
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• pp.53-60
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• 2015

For high-accuracy position control of a linear motor, it has been proposed a nonlinear controller including a synchronization algorithm. Linear motors are easily affected by force ripple, friction, and parameter variations because there is no mechanical transmission to reduce the effects of model uncertainties and external disturbances. Synchronization error is also caused by skew motion, model uncertainties, and force disturbance on each axis. Nonlinear effects such as friction and ripple force are estimated and compensated for. The synchronization algorithm is used to reduce the synchronous error of the two side pillars. The performance of the controller is evaluated by computer simulations.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1990년도 가을 학술발표회 논문집
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• pp.95-100
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• 1990

An optimization method has been developed to find the minimum weight design of steel building structures which consist of the commercially available discrete sections. In this study, an emphasis was particularly placed on the practical applicability of optimization algorithm in engineering practice. The structure Is optimized through element optimization under the element level constraints first and then, if there is any violation of structural level constraints, it is adequately compensated by the constraint error correction vector obtained through the sensitivity analysis. A scaling procedure is introduced for the problems of large violated displacement constraint. The oscillation control in the objective function is also discussed. By dividing the available H-sections into two groups based on their section characteristics, much improved relationships between section variables were obtained and used efficiently in searching the optimum section in the section table.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1993년도 춘계학술대회
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• pp.81-85
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• 1993

Despite the simplicity of processing, conventional autocorrelation function (ACF) method for the precise determination of fetal heart rate (FHR) has many problems. In the case of weak or noise corrupted Doppler ultrasound singnals, the ACF method is very sensitive to the threshold level and data window length. It is real troublesome to extract FHR when there is a data loss. To overcome these problems, the high resolution pitch detection algorithm is adapted to estimate the FHR. The FHR is determined from the correlation of two interconnected segments by its maximum correlation value. FHR is compensated with a constant correlation threshold in a greatly smeared noise signal. This method yields more accurate, robust and reliable than the ACF method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.77-79
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• 2007

The phase angle of the utility voltage is used in current control of grid-tied fuel cell power converter. Therefore if the detection of phase angle is a problem, Current control is affected by the distorted phase angle. This paper presents a problem of synchronous reference frame PLL algorithm for single-phase systems and proposes compensated synchronous reference frame PLL algorithm. The proposed method helps power quality improvement of grid-tied fuel cell power converter under distorted utility conditions. Simulation and experimental results are presented to demonstrate the validity of the proposed method.

• 한국군사과학기술학회지
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• 제16권4호
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• pp.566-574
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• 2013

In this paper, direct power control system for three-phase PFC AC/DC converter without the source voltage sensors is proposed. The sinusoidal input current and unity effective power factor are realised based on the estimated flux in the observer. Both active and reactive power calculated using estimated flux. The estimation of flux is performed based on the reduced-order virtual flux observer using the actual currents and the command control voltage. Moreover, source voltage sensors are replaced by a estimated flux. DC output voltage has been compensated by DC output ripple voltage estimation algorithm. The active and reactive powers estimation are performed based on the estimated flux and Phase angle. The proposed algorithm is verified through simulation and experiment.

• ETRI Journal
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• 제43권4호
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• pp.684-693
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• 2021

This paper presents a low-cost two-stage approximate multiplier for bfloat16 (brain floating-point) data processing. For cost-efficient approximate multiplication, the first stage implements Mitchell's algorithm that performs the approximate multiplication using only two adders. The second stage adopts the exact multiplication to compensate for the error from the first stage by multiplying error terms and adding its truncated result to the final output. In our design, the low-cost multiplications in both stages can reduce hardware costs significantly and provide low relative errors by compensating for the error from the first stage. We apply our approximate multiplier to the convolutional neural network (CNN) inferences, which shows small accuracy drops with well-known pre-trained models for the ImageNet database. Therefore, our design allows low-cost CNN inference systems with high test accuracy.

• 한국산업융합학회 논문집
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• 제22권4호
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• pp.435-445
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• 2019

Ball screw drives are widely used in industry, and many studies have been devoted on precise, fast and robust control of ball screw drives. In this study, a novel position control algorithm for ball screw drives is proposed, which consist of a PD controller, a friction feedforward and a disturbance observer. The dynamics and the position error of such controller are analyzed to establish an error model, which can be used to predict the resulting position error of the given desired trajectory. Using the proposed error model, the desired trajectory can be modified so that the predicted position error can be compensated in a feedforward manner. The proposed algorithm does not require the model of the system for the error prediction, and thus can be easily applied to conventional control systems. The performance of the system is verified through simulations and experiments.

• Journal of Power Electronics
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• 제19권4호
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• pp.1045-1053
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• 2019

A symmetrical component decomposition scheme utilizing the characteristics of the asynchronous rotational reference frame transformation is proposed in this paper for the extraction of the positive and negative sequence components of distorted three-phase grid voltages. The undesired frequency component can be removed using a specially designed series coordinate transformation and half-cycle delays, where the delay can be controlled by adjusting the frequency of the rotating reference frame. The extracted symmetrical component can then be compensated based on the applied coordinated transformation. The dynamic response of the proposed algorithm is improved when compared to that of conventional methods. The effectiveness of the proposed algorithm is verified by simulation and experimental results.