• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.555-564
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• 2017

In this paper, a new technique for attitude and heading reference system (AHRS) using low-cost MEMS sensors of the gyroscope, accelerometer, and magnetometer is addressed particularly in vibration environments. The motion of MEMS sensors interact with the scale factor and cross-coupling errors to produce random errors by the harsh environment. A new adaptive attitude estimation algorithm based on the Kalman filter is developed to overcome these undesirable side effects by analyzing windowed measurement error covariance. The key idea is that performance degradation of accelerometers, for example, due to linear vibrations can be reduced by the proposed measurement error covariance analysis. The computed error covariance is utilized to the measurement covariance of Kalman filters adaptively. Finally, the proposed approach is verified by using numerical simulations and experiments in an acceleration phase and/or vibrating environments.

• 한국컴퓨터정보학회논문지
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• 제14권6호
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• pp.41-49
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• 2009

본 논문에서는 광학식 모션캡처 장비를 위한 다중 카메라 보정 방법을 제안한다. 이 방법은 DLT(Direct linear transformation) 알고리즘을 이용하여 7개의 마커가 있는 3축 보정틀의 영상을 획득하여 1차 카메라 보정을 한다. 그리고 2개의 마커가 있는 보정봉을 측정하고자 하는 영역에서 움직여서 2차 카메라 보정을 실시한다. 1차 카메라 보정에서는 카메라 보정뿐만 아니라 렌즈 왜곡 계수를 계산하여 2차 카메라 보정에서의 최적화를 위한 초기해로 사용한다. 2차 카메라 보정에서는 보정봉에 있는 마커사이의 거리가 일정하기 때문에 계산된 마커 거리와 실제 마커 거리의 차가 최소화 되도록 최적화를 수행한다. 제안한 방법에 의한 다중 카메라 보정 방법을 검증하기 위하여 재투영에러를 계산하였고 3축 보정틀에 있는 마커사이의 거리와 보정봉에 있는 마커사이의 거리를 계산하여 다른 상용장비의 값과 비교하였다. 3축 보정틀에 있는 마커를 복원하여 에러를 비교한 결과 평균오차가 상용장비의 1.7042mm에 비해 0.8765mm로 51.4% 수준으로 나타났고, 보정봉에 있는 마커를 복원하여 에러를 비교한 결과 상용장비의 평균에러 1.8897mm에 비해 2.0183mm로 0.1286mm 크게 나타났다.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1718-1729
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• 1997

This paper describes motion errors due to acceleration and deceleration types of servo motors in NC machine tools. Motion errors are composed of two components : one is due to transient response of a servomechanism and the other comes from gain mismatching of positioning servo motors. It deals with circular interpolation to identify motion errors by using Interface card. Also in order to minimize motion errors, this study presents an effective method to optimize parameters which are connected with motion errors. The proposed method is based upon a second order polynomial regression model and it includes an orthogonal array method to make the effective results of experiments. The validity and reliability of the study were verified on a vertical machining center equipped with FANUC 0MC through a series of experiments and analysis.

• 한국통신학회논문지
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• 제29권9C호
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• pp.1330-1336
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• 2004

본 논문에서는 동영상 부호화 기의 성능을 개선하기 위한 최소 자송 기반 적응 움직임 벡터 예측 알고리즘을 제안 하고자 한다. 적응 움직임 벡터 예측 방식은 동영상 움직임 벡터의 국부 통계적인 특성의 돌연한 변화로 특정지어 진다는 것을 바탕으로 최소 자승(Least Squared) 기반의 선형 움직임의 계수들을 통계적 특성에 따라 최적화하는 방식이지만 상기 방식은 애우 높은 계산 량을 요구하는 단정을 지니고 있다. 본 논문에서는 공간적인 움직임 변화 방향성을 가지는 최소 자승 최적화를 기반으로 움직임 예측기의 계수를 적응적으로 조절하여 움직임 예측 오류뿐만 아니라 계산 량도 감소시키는 방식에 대해 기술한다. 실험을 통해 제안된 방식의 성능을 확인할 수 있었다.

• Structural Engineering and Mechanics
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• 제70권3호
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• pp.289-301
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• 2019

Hysteretic energy is defined as energy dissipated through inelastic deformations during a ground motion by the system. It includes frequency content and duration of ground motion as two remarkable parameters, while these characteristics are not seen in displacement spectrum. Since maximum displacement individually cannot be the appropriate criterion for damage assessment, hysteretic energy has been evaluated in this research as a more comprehensive seismic demand parameter. An innovative methodology has been proposed to establish a new equivalent linear model to estimate hysteretic energy spectrum for bilinear SDOF models under two different sets of earthquake excitations. Error minimization has been defined in the space of equivalent linearization concept, which resulted in equivalent damping and equivalent period as representative parameters of the linear model. Nonlinear regression analysis was carried out for predicting these equivalent parameter as a function of ductility. The results also indicate differences between seismic demand characteristics of far-field and near-field ground motions, which are not identified by most of previous equations presented for predicting seismic energy. The main advantage of the proposed model is its independency on parameters related to earthquake and response characteristics, which has led to more efficiency as well as simplicity. The capability of providing a practical energy based seismic performance evaluation is another outstanding feature of the proposed model.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.379-380
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• 2007

In this paper, we propose the fast hi-linear interpolation method for SR reconstruction. This method reconstructs the HR image rapidity by considering motion vector information for each LR input image. And its calculation used normalized deviation of image data. As using the motion vector information which is obtained at registration error checking process, this proposed can be achieved the fast and simple SR reconstructed image.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3709-3715
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• 2023

It is an important work to measure the dimensions of underwater spent fuel assemblies in the nuclear power industry during the overhaul, to judging whether the spent fuel assemblies can continue to be used. In this paper, a three dimensional reconstruction method for underwater spent fuel assemblies of nuclear reactor based on linear structured light is proposed, and the topography and size measurement was carried out based on the reconstructed 3D model. Multiple linear structured light sensors are used to obtain contour size data, and the shape data of the whole spent fuel assembly can be collected by one-dimensional scanning motion. In this paper, we also presented a corrected model to correct the measurement error introduced by lead-glass and water is corrected. Then, we set up an underwater measurement system for spent fuel assembly based on this method. Finally, an underwater measurement experiment is carried out to verify the 3D reconstruction ability and measurement ability of the system, and the measurement error is less than ±0.05 mm.

• 드라이브 ㆍ 컨트롤
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• 제9권4호
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• pp.1-7
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• 2012

The voice coil linear force motor is a kind of a direct drive motion device that uses a permanent magnetic field and coil winding to produce force. In order to design a voice coil linear force motor, an exact calculations of the required force, the flux density in air gap and the flux pathway are needed. A conventional method can be used usually to calculate the flux density in air gap, but with this method it is needed to find a magnetic circuit revision constant. In this paper a voice coil linear force motor is designed by conventional design method and analyzed by 3D simulation program "Flux". For the prototype linear force motor, the results of the calculated by conventional design method and the analyzed by 3D simulation program are compared with the test result. Finally it is showed that the magnetic circuit revision constant which is found by comparing of the analyzed and the measured data can be used for the design of the voice coil type linear force motor to minimize the trial and error.

• 한국정밀공학회지
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• 제21권3호
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• pp.155-162
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• 2004

This paper presents the fabrication procedure and the experiments for the 3-axis fine positioning stage proposed in［1］. First, the dynamic characteristics of the actuator and the stage are tested with the preload changed in order to validate the stage design specifications. Secondly, the performance of the stage is also evaluated on the accuracy associated with linear positioning, angular error, and straightness error. Experimental results show that the developed stage is accurate enough to be used for nanometer positioning. Through the analysis and experiment, the developed fine positioning stage are found to have a long stroke due to the magnetically preloaded PZT actuators, the minimum motion crosstalk due to the use of a ball contact mechanism and the compact design.

• 센서학회지
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• 제28권3호
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• pp.146-151
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• 2019

This paper reports a sliding window filtering approach for ground moving targets with cross-correlated sensor noise and uncertainty. In addition, the effect of uncertain parameters during a tracking error on the model performance is considered. A distributed fusion sliding window filter is also proposed. The distributed fusion filtering algorithm represents the optimal linear combination of local filters under the minimum mean-square error criterion. The derivation of the error cross-covariances between the local sliding window filters is the key to the proposed method. Simulation results of the motion of the ground moving target a demonstrate high accuracy and computational efficiency of the distributed fusion sliding window filter.