• International Journal of Aeronautical and Space Sciences
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• 제16권1호
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• pp.102-109
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• 2015

In Korea, Lunar exploration program has been prepared with the aim of launching in the 2020's. As a part of it, a lunar lander demonstrator was developed, which was the model for verifying the system such as structure, propulsion, and control system, before launching into the deep space. This paper deals with the path tracking performance of the lunar lander demonstrator with respect to the thruster controller based on Pulse Width Pulse Frequency Modulator (PWPFM) and Pulse Width Modulator (PWM). First, we derived equations of motion, considering the allocation of the thrusters, and designed the path tracking controller based on Euler angle. The signal generated from the path tracking controller is continuous, so PWPFM and PWM modulator are adopted for generating ON/OFF signal. Finally, MATLAB simulation is performed for evaluating the path tracking ability. We compared the path tracking performances of PWPFM and PWM based thrust controller, using performance measures such as the total impulse and the position error with respect to the desired path.

• ETRI Journal
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• 제37권3호
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• pp.617-625
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• 2015

In this paper, a steering control system for the path tracking of autonomous vehicles is described. The steering control system consists of a path tracker and primitive driver. The path tracker generates the desired steering angle by using the look-ahead distance, vehicle heading, and a lateral offset. A method for applying an autonomous vehicle to path tracking is an advanced pure pursuit method that can reduce cutting corners, which is a weakness of the pure pursuit method. The steering controller controls the steering actuator to follow the desired steering angle. A servo motor is installed to control the steering handle, and it can transmit the steering force using a belt and pulley. We designed a steering controller that is applied to a proportional integral differential controller. However, because of a dead band, the path tracking performance and stability of autonomous vehicles are reduced. To overcome the dead band, a dead band compensator was developed. As a result of the compensator, the path tracking performance and stability are improved.

• 한국지능시스템학회논문지
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• 제22권2호
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• pp.225-231
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• 2012

본 논문에서는 접근 각도 개념을 이용하여 과소작동기 형태의 무인 수중 잠수정의 경로 추적 제어기 설계 방법을 제안한 다. 과소 작동기 형태를 가지는 무인 수중 잠수정은 종 방향 추진력과 회전력에 의해 속도와 방향을 조절하나, 횡 방향 추 진기가 없기 때문에 횡 방향에 대한 움직임을 제어 할 수 없다. 이러한 무인 수중 잠수정의 과소 작동기 문제를 해결하기 위하여 본 논문에서는 기준 경로에 대한 접근 각도 개념을 제안하고, 제안한 접근 각도를 이용하여 경로 추적 제어기를 설 계한다. 이를 위해 동체 고정 좌표계에서 새로운 오차 방정식을 구하고, 리아푸노프 방법을 기반으로 경로 추적 제어기를 설계한다. 본 논문에서는 컴퓨터 시뮬레이션 통해 제안한 방법에 의해 설계된 제어기의 성능을 검증한다.

• 한국해양환경ㆍ에너지학회지
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• 제2권1호
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• pp.90-101
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• 1999

본 논문은 선박자동 항로 추적제어기와 자동접이안 제어기를 포함하는 선박자동운항시스템 설계와 관련이 있다. 자동항로 추적제어기의 설계를 위해서는 최적제어기가 사용되었는데 선형화된 선박조종식이 사용되었다. 수치예는 자동항로 추적제어기가 선장이 미리정한 way point를 추적할 수 있음을 보여주고 있다. 자동접이안 제어기의 설계를 위해서는 비중앙화 방식의 제어기가 사용되었다. 자동접이안 제어기는 자동 항로 추적 제어기에 전진속도에 대한 퍼지 로직 제어기가 추가 되어 실현되었다 수치예는 자동접이안 제어기가 성공적으로 사용되었음을 보여준다.

• 로봇학회논문지
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• 제10권3호
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• pp.154-161
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• 2015

Conventional path tracking methods designed for two-wheeled differential drive robots are not suitable for omni-directional robots. In this study, we present a controller which can accomplish more accurate path tracking and orientation correction by exploiting the unconstrained movement capability of omni-directional robots. The proposed controller is proven to be stable using a Lyapunov stability criterion. Various experiments in real environments show that performance of path tracking and orientation correction has improved in the proposed controller.

• 한국항공운항학회지
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• 제22권4호
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• pp.75-80
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• 2014

A lunar lander demonstrator developed for the purpose of demonstrating lunar landing technologies recently in Korea. The thruster control system of the lunar lander demonstrator adopted the main thrusters for altitude control and the reaction thrusters for attitude control. In this paper, we propose a path tracking controller base on Euler angles. The control signals of the controller are of continuous type. And Pulse Width Modulator(PWM) is adopted to provide On/Off signals. We perform MATLAB simulation for evaluating the path tracking performance and the final landing velocity of the lunar lander demonstrator.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.335-336
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• 2013

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2473-2475
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• 2001

In trajectory tracking methods, the error values of current position and velocity are compensated to follow the given reference path and velocity. The path tracking for a wheeled mobile robot is treated in this paper. It is very difficult to implement stable trajectory tracking algorithms because mobile robots have kinematically non-holonomic constraints. For solving this problem, a velocity controller is presented in this paper. This velocity controller is designed by a PID controller which could be easily employed. In this case, velocity errors caused by system uncertainties or internal and external disturbances could exist. A neural network is used for compensating the velocity errors. Input variables of this neural network compensator are defined by differences between the velocities of the posture controller and the real velocities of the mobile robot. Simulation results show the effectiveness of the proposed controller.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.512-515
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• 1997

In this paper the fuzzy-genetic controller for path-tracking of WMRs is proposed. Fuzzy controller is implemented to adaptive adjust the crossover rate and mutation rate, and genetic algorithm is implemented to adaptive adjust the control gain during the optimization. The computer simulation shows that the proposed fuzzy-genetic controller is effective.

• 한국정밀공학회지
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• 제28권11호
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• pp.1265-1271
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• 2011

These days the number of aged and disabled people is increasing rapidly. But most of the disabled or the aged who have the ability to work, want to engage in economic activities and solve social restrictions as well as their bad financial conditions. This paper concerns about the tracking control of an electric wheelchair robot for welfare vehicle where the seat and electric wheelchair are separated and electric wheelchair robot must be autonomously controlled without the help of assistant. So the aged or the disabled people can drive welfare vehicle by himself by adopting this system. Therefore the concept of both an autonomous driving of electric wheelchair and path tracking robots is required in this system. Finally we suggested fuzzy controller in order to control the path tracking of electric wheelchair robot and compared the capability of the proposed controller with conventional PID controller.