• 한국정밀공학회지
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• 제22권7호
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• pp.102-111
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• 2005

In this paper, we address a position control for a parallel stage, which is levitated and driven by electric magnetic force. This consists of a levitating object (called platen) with 4 permanent magnetic linear synchronous motors in parallel. Each motor generates vertical force for suspension against gravity and propulsion force horizontally as well. This stage can generate six degrees of freedom motion by the vertical and horizontal force. A dynamic equation of the stage system is derived based on Newton-Euler method and it's special Jacobian matrix describing a relation between the limited velocity and Cartesian velocity is done. There are proposed two control methods for positioning which are Cartesian space controller and Actuator space controller. The control performance of the Cartesian space controller is better than the Actuator space controller in task space trajectory while the Actuator space controller is simpler than the Cartesian space controller in controller realization.

• 한국전자파학회논문지
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• 제30권1호
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• pp.38-44
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• 2019

본 논문에서는 자기 공진형 무선전력전송 시스템에서 사용 가능한 핑거프린트 방식의 측위 기법을 제안하고 성능을 검증하였다. 측위를 위해 3축 방향의 자기장 신호 측정이 가능한 소형 직교 보조코일을 가지는 수신기 코일 설계 방안을 제시하고, 제안한 코일을 이용해 획득한 3축의 기전력의 크기와 위상 특성을 추출하였다. 측정 지점에서 획득된 값을 이용하여 위치를 측정하기 위해 LUT(Look-up Table)를 이용하는 기법과 기계학습 방식 중 LDA(Linear Discriminant Analysis)을 이용하는 기법을 제안하고, 각 기법별 측위 정확도 및 계산 속도를 비교 제시하였다. 6.78 MHz 무선전력전송시스템에서 75개의 지점을 측위하는 실험에서 제안하는 코일과 기전력 특성을 이용한 LUT 기법을 적용하여 측위 정확도 97.33%를 달성하였다. LDA 기법의 경우, 기전력과 위상을 이용하여 측위하는 경우 LUT 기법에 비해 계산 속도가 늘어나지만 정확도를 향상시킬 수 있었다.

• IEIE Transactions on Smart Processing and Computing
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• 제6권1호
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• pp.1-9
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• 2017

This paper proposes to improve the performance of a strap down inertial navigation system using a foot-mounted low-cost inertial measurement unit/magnetometer by configuring an attitude and heading reference system. To track position accurately and for attitude estimations, considering different dynamic constraints, magnetic measurement and a zero velocity update technique is used. A conventional strap down method based on integrating angular rate to determine attitude will inevitably induce long-term drift, while magnetometers are subject to short-term orientation errors. To eliminate this accumulative error, and thus, use the navigation system for a long-duration mission, a hybrid configuration by integrating a miniature micro electromechanical system (MEMS)-based attitude and heading detector with the conventional navigation system is proposed in this paper. The attitude and heading detector is composed of three-axis MEMS accelerometers and three-axis MEMS magnetometers. With an absolute algorithm based on gravity and Earth's magnetic field, rather than an integral algorithm, the attitude detector can obtain an absolute attitude and heading estimation without drift errors, so it can be used to adjust the attitude and orientation of the strap down system. Finally, we verify (by both formula analysis and from test results) that the accumulative errors are effectively eliminated via this hybrid scheme.

• Journal of Astronomy and Space Sciences
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• 제36권3호
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• pp.181-186
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• 2019

The attitude information of spacecraft can be obtained by the sensors attached to it using a star tracker, three-axis magnetometer, three-axis gyroscope, and a global positioning signal receiver. By using these sensors, the spacecraft can be maneuvered by actuators that generate torques. In particular, electromagnetic-torque bars can be used for attitude control and as a momentum-canceling instrument. The spacecraft momentum can be created by the current through the electrical circuits and coils. Thus, the current around the electromagnetic-torque bars is a critical factor for precisely controlling the spacecraft. In connection with these concerns, a solar-cell array can be considered to prevent generation of a magnetic dipole moment because the solar-cell array can introduce a large amount of current through the electrical wires. The maximum value of a magnetic dipole moment that cannot affect precise control is $0.25A{\cdot}m^2$, which takes into account the current that flows through the reaction-wheel assembly and the magnetic-torque current. In this study, we designed a 300-W solar cell array and presented an optimal wire-routing method to minimize the magnetic dipole moment for space applications. We verified our proposed method by simulation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.894-897
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• 2004

In this paper, we address a position control scheme for a stage system, which is levitated and driven by electric magnetic actuators. This consists of a levitating object (called platen) with 4 permanent magnetic linear synchronous motors in parallel. Each motor generates vertical force for suspension against gravity and propulsion force horizontally as well. This stage can generate six degrees of freedom motion by the vertical and horizontal forces. Dynamic equations of the stage system are derived based on Newton-Euler method and its special Jacobian matrix describing a relation between the Joint velocity and platen velocity is done. There are proposed two control schemes for positioning, which are Cartesian space controller and Joint space controller. The control performance of the Cartesian space controller is better than the Joint space controller in task space trajectory while the Joint space controller is simpler than the Cartesian space controller in controller realization.

• 한국통신학회논문지
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• 제39A권9호
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• pp.514-518
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• 2014

트랙을 겹쳐서 쓰는 자기기록 방식은 인접한 트랙간 간섭이 심하게 발생한다. 또한 리드헤드가 트랙을 따라 돌면서 데이터를 읽을 때, 물리적인 영향으로 헤드가 틀어질 수 있다. 본 논문에서는 이러한 문제들을 해결하기 위해 두 개의 헤드를 사용하는 이차원 이퀄라이저를 제안하였다. 헤드가 틀어진 경우 두 헤드의 위치를 현재 트랙의 중앙에 위치시킴으로 성능을 보완할 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 D
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• pp.2576-2578
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• 2005

In this paper, we address two position control scheme; the lead-lag control and the sliding mode control for a stage system, which is levitated and driven by electric magnetic actuators. This consists of a levitating object (called platen) with 4 permanent magnetic linear synchronous motors in parallel. Each motor generates vertical force for suspension against gravity and propulsion force horizontally as well. The sliding mode control algorithm is more effective than the lead-lag control algorithm to reduce effects from movements and disturbances of other axis.

• 한국정밀공학회지
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• 제20권10호
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• pp.47-55
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• 2003

In the development of positioning device for precision manufacturing and measuring, the friction from mechanical contact causes serious decrease of performance. In this study, we studied about variable reluctance type contact-free linear actuator to overcome drawbacks from friction. In the view of electromagnetics, we analyzed and derived theoretical magnetic force equation and designed structure for generating suspension and propulsion force simultaneously. In the view of dynamics, we derived equation of motion and identified the stability of the system. Finally, we verified the feasibility of the proposed system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.428-428
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• 2000

A robust intelligent algorithm for AGV navigation control is presented here based on both magnetic and gyro sensors to track a reference trajectory. Since the proposed system uses an intermittent array of short magnetic tape strips, it lends itself to a very easy installation and maintenance compared to other types of positioning references such as electric wire, magnets, RF and laser beacons. The neural network is to predict the lateral deviation of the AGV in the intervals where no magnetic tape references are available. Further, the use of intelligent control ensures a robust and flexible control performance. Computer simulation of AGV control demonstrates its adequate tracking performances even where the sensor information is not available. Real experiments using Samsung AGV are also on the way for real verification

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.191-193
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• 2006

The ionospheric strom evolution process was monitored during the 18 August 2003 magnetic strom over China, through inversion of the ionospheric electron density from GPS observations. The temporal and spatial variations of the ionosphere were analysed as a time series of ionospheric electron density profiles. Results show that the main ionospheric effects of the storm over China under consideration are: the positive storm phase effect usually happens in the low latitudinal ionospheric; the negative storm phase effect occurs in the middle latitude, and the equatorial anomaly structure can be found as well.