• International Journal of Aeronautical and Space Sciences
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• v.16 no.1
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• pp.77-88
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• 2015

The dynamics of relative motion in a perturbed orbital environment are exploited based on Gauss' and Cowell's variational equations. The inertial coordinate frame and relative coordinate frame (Hill frame) are used, and a linear high fidelity model is developed to describe the relative motion. This model takes into account the primary gravitational and atmospheric drag perturbations. Then, this model is used in the design of a navigation, guidance, and control system of a chaser vehicle to approach towards and to depart from a target vehicle in proximity operations. Relative navigation uses an extended Kalman filter based on this relative model to estimate the relative position/velocity of the chaser vehicle with respect to the target vehicle. This filter uses the range and angle measurements of the target relative to the chaser from a simulated LIDAR system. The corresponding measurement models, process noise matrix, and other filter parameters are provided. Numerical simulations are performed to assess the precision of this model with respect to the full nonlinear model. The analyses include the navigation errors and trajectory dispersions.

• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.59-74
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• 2009

Relative navigation system is presented using GPS measurements from a single-channel global positioning system (GPS) simulator. The objective of this study is to provide the real-time inter-satellite relative positions as well as absolute positions for two formation flying satellites in low earth orbit. To improve the navigation performance, the absolute states are estimated using ion-free GRAPHIC (group and phase ionospheric correction) pseudo-ranges and the relative states are determined using double differential carrier-phase data and singled-differential C/A code data based on the extended Kalman filter and the unscented Kalman filter. Furthermore, pseudo-relative dynamic model and modified relative measurement model are developed. This modified EKF method prevents non-linearity of the measurement model from degrading precision by applying linearization about absolute navigation solutions not about the priori estimates. The LAMBDA method also has been used to improve the relative navigation performance by fixing ambiguities to integers for precise relative navigation. The software-based simulation has been performed and the steady state accuracies of 1 m and 6 mm ($1{\sigma}$ of 3-dimensional difference errors) are achieved for the absolute and relative navigation using EKF for a short baseline leader/follower formation. In addition, the navigation performances are compared for the EKF and the UKF for 10 hours simulation, and relative position errors are mm-level for the two filters showing the similar trends.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.215-219
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• 2003

In this paper, we generate a trajectory minimized the energy gait of a biped robot for walking a staircase using genetic algorithms and apply to the computed torque controller for the stable dynamic biped locomotion. In the saggital plane, a 6 degree of freedom biped robot that model consists of seven links is used. In order to minimize the total energy efficiency, the Real-Coded Genetic Algorithm (RCGA) is used. Operators of genetic algorithms are composed of a reproduction, crossover and mutation. In order to approximate the walking gait, the each joint angle is defined as a 4-th order polynomial of which coefficients are chromosomes. Constraints are divided into equality and inequality. Firstly, equality constraints consist of position conditions at the end of stride period and each joint angle and angular velocity condition for periodic walking. On the other hand, inequality constraints include the knee joint conditions, the zero moment point conditions for the x-direction and the tip conditions of swing leg during the period of a stride for walking a staircase.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.541-542
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• 2011

최근 산업현장에서 작업의 정밀도에 대한 요구가 높아지면서 산업용 로봇의 정밀위치제어에 대한 연구가 활발히 이루어지고 있다. 특히 정밀 위치제어가 요구되는 산업용 로봇에서 외란은 로봇의 성능에 영향을 미치는 중요한 요소 중의 하나이다. 본 논문에서는 다관절 로봇에 사용되는 AC서보 모터의 고강성 정밀 위치제어를 위해 외란 변화에 대한 강인한 제어를 할 수 있는 외란 관측기와 파라메터 변동에 따른 보상 알고리즘을 제안하였다. 제안된 알고리즘은 시뮬레이션과 실험을 통해 외란 변화에 대해 정밀한 위치제어가 가능함을 보였다. 또한, 다관절 로봇의 각 축에 적용되고 있는 AC서보 모터의 PID 제어기와 제안된 알고리즘과의 비교를 통해 부하 변동에 따른 두 제어기의 차이점을 보였다.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1640_1641
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• 2009

Dynamic friction and force ripple are the most predominant factors that affect the positioning accuracy of permanent magnet synchronous motor(PMSM) servo drives system, and it is desirable to compensate them in finite time with a continuous control law. In this paper, based on LuGre dynamic friction model, a robust adaptive skidding mode controller is proposed to compensate the nonlinear effect of friction and force ripple. The controller scheme consists of a PD component and a robust adaptive sliding mode controller for estimating the unknown system parameter. Using Lyapunov stability theorem, asymptotic stability analysis and position tracking performance are guaranteed. Simulation results well verify the feasibility and the effectiveness of the proposed scheme for high0precision motion trajectory tracking.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.888-893
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• 2005

Since inertial sensor errors which increase with time are caused by initial orientation error and sensor errors(accelerometer bias and gyro drift bias), the accuracy of these devices, while still improving, is not adequate for many of today's high-precision, long-duration sea, aircraft, and long-range flight missions. This paper presents a navigation error compensation scheme for Strap-Down Inertial Navigation System(SDINS) using star tracker. To be specific, SDINS error model and measurement equation are derived, and Kalman filter is implemented. Simulation results show the boundedness of position and attitude errors.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.115-118
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• 2001

일반적으로 반도체 제조 공정은 매우 복잡하고 다양한 공정들로 구성된다. 이러한 공정 중 Stage 부분은 웨이퍼에 회로 패턴을 기입하기 위하여 웨이퍼를 미리 지정된 위치로 이송하는 공정으로 매우 높은 정밀도가 요구되고 있다. Stage에 대해서는 x, y, z축 뿐아니라 각 축에 대한 회전까지도 고려한 6축 제어가 수행되어야 한다. 본 논문에서는 stage에 대한 정밀제어의 기반기술로서 선형 BLDC 모터를 이용하여 1축 위치제어 시스템의 제어에 관하여 연구하였다. 선형 BLDC 모터의 이동 중 발생하는 추럭리플을 보상하여 제어기 설계시 선형 시스템으로 고려하여 제어기를 설계할 수 있도록 하는 방법을 제안하였으며 실험을 통하여 1[${\mu}m$]의 해상도를 갖는 위치검출 엔코더를 이용하여 5[${\mu}m$]의 정밀도를 얻을 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.776-778
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• 2003

In the paper, the novel linear ultrasonic motor for precision position control was designed and fabricated. It was composed of two piezoelectric actuators with longitudinal ultrasonic fluctuations and shaking beam. When two AC electric fields ($Usin{\omega}t$, $Ucos{\omega}t$) were applied in two piezoelectric actuators respectively, the middle part of shaking beam had an elliptical trajectory. According to experimental results, good symmetrical characteristic of two piezoelectric actuators were obtained.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.564-566
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• 1992

It is tragic that the Korean Airline Boing 747, KE007, wandered hundreds of miles off course into Soviet airspace and was shot down on September 1, 1983. The exact cuases are not known yet. Thus, speculation centers on human error or faulty procedure of three Litton LTN-72R inertial navigation systems(INS) with which the KAL KE007 was equipped. The inertial platform must be aligned before the INS can be used as a precision inertial navigation system. This analysis checks a possibility that the navigation errors are caused by a wrong INS alignment procedure assuming it is done at Anchorage. Possible causes for the navigational position error, such as alignment errors and gyro drift errors, are analyzed through inertial navigation system error prapagation simulations. A set of misalignment angle is estimated to determine what degree of alignment errors are required to cause the navigation error assuming that the accident is caused by the INS misalignment.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.903-908
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• 2005

Existing ATC/ATO/TWC system has a ATC(Automatic Train Control) antenna for receiving the speed code, a ATO(Automatic Train Operation) antenna for obtaining the exact distance to go to platform and TWC(Train and Wayside Communication) antenna for communication between on-board and wayside system. This paper proposes the ATO/TWC antenna with tele-powering module, telegram transmitter/receiver module. This antenna communicates with a passive type tag(wayside Precision Stop Marker) for the information of distance from the stop position and a active type tag for the door command and status in the platform.