• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.146-155
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• 2009

This paper considers the path tracking problem in a horizontal plane for underactuated (or non-holonomic) autonomous underwater vehicles (AUVs). Underwater mapping has been an important mission for AUVs. Recently, underwater docking has also become a main research field of AUVs. These kinds of missions basically require accurate attitude and trajectory control performance. However, the non-holonomic problem should be solved to achieve accurate path tracking for the torpedo-type of AUVs. In this paper, resolved motion and acceleration control (RMAC) is considered as a path tracking controller for an underactuated torpedo-shaped AUV, ISiMi. A set of numerical simulations is carried out to illustrate the effectiveness of the proposed RMAC scheme, and experimental data with ISiMi100 and discussions are presented.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.3
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• pp.28-34
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• 2014

In this paper, we propose a trajectory tracking controller for a two-wheeled mobile robot (WMR) with nonholonomic constraints using a fuzzy sliding-mode controller-based hyperbolic function. The proposed controller is composed of two separate controllers. The sliding-mode controller is used for attitude control of the WMR, and the fuzzy controller-based hyperbolic function is designed to adjust the reach time of the sliding-mode control. Simulation results on a linear and a circular trajectory show that the proposed controller improves the control performance. The proposed controller reduces the reach time by as much as 47% compared to the controller proposed by Xie et al.

• Proceedings of the Korea Society for Simulation Conference
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• 1997.04a
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• pp.45-60
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• 1997

본연구의 목적은 1994년과 1995년의 연구 결과를 토대로 고속국도 교통류의 차량 추종, 차선 변경 특성을 현장 조사 자료를 통하여 분석·규명하고, 국내 고속도로의 교통류 특성을 반영할 수 있는 한국형 고속국도 모의실험 모형을 개발하는데 있다. 본 연구의 주요 결과는 다음과 같다. ▶ 국내 고속국도 교통류의 차두시간, 속도, 차량군의 크기, 차선 변 경, 중차량의 영향 등의 특성을 조사·분석하여 관련 매개변수와 모형식을 도출하였다. ▶ 차량 생성 모형은 개별 차량의 차두시간, 속도를 이용하여 구축하였으며, 중차량의 구성 비 율에 따른 속도 변화를 연구하여 그 결과를 모형 구축에 응용하였다. ▶ 차량 추종 모형은 1995년 연구에서 검증된 PITT-KLD 모형에 기반을 두었으며, 현장 실측 자료를 분석하여 차량 추종과 관련된 매개변수들을 설정하였다. ▶ 차선 변경 모형은 기본적으로 간격 수락 모형을 이용하였으며, 차선 변경시 임계 간격을 국내 운전자들의 유형에 따라 10가지로 설 정하였다. 차선 변경 확률은 현장 조사 자료를 기초로 한 경험적 모형을 구축하여 선정하였 으며, 마코프 연쇄 기법과도 비교·검토하였다. ▶ 개발된 모의실험 모형을 비교·평가하기 위 해 고속국도 합류부의 현장 조사 자료와 모의실험 모형을 비교·평가한 결과, 합류 이전 단 계에서는 실측치와 모형의 통계량이 어느 정도 유사한 양상을 보이지만 합류 이후 단계에서 는 차이를 나타내고 잇다.

• Journal of Ocean Engineering and Technology
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• v.30 no.1
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• pp.32-43
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• 2016

A UUV needs to have a robust path following performance because of unpredicted current disturbances. Because the desired path of a UUV is usually designed by considering the locations of obstacles or geographical features of the operation region, the UUV should stay on the desired path to avoid damage or loss of the vehicle. However, conventional path following methods cannot deal with strong countercurrent disturbances. Thus, the UUV may deviate from the desired path. In order to avoid such deviation, a backward path following method is suggested. This paper proposes a path following method that combines pure pursuit guidance and nonlinear guidance for the UUV under an unpredicted strong ocean current. For a stable path following system, this paper suggests that the UUV adjust its heading to the current direction using the pure pursuit guidance method when the system is in an unstable region, or the UUV follows the desired path with nonlinear guidance. By combining the pure pursuit guidance and nonlinear guidance, it was possible to overcome the drawbacks of each path following method in the reverse path following case. The efficiency of the proposed method is shown through simulation results compared to those of the pure pursuit method and nonlinear guidance method.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2417-2419
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• 2003

이동성에 nonholonomic 제약을 받는 차륜 구동 이동 로봇의 불확실한 환경에서의 자율 주행 제어기를 제안하였다. 전체 시스템은 on-line으로 지역경로 계획을 하는 planner 부분과 차륜 구동 이동 로봇의 nonholonomic 제약을 극복하면서 계획된 지역 경로를 충실히 추종하기 위한 제어기 부분의 두 부분으로 구성하였다. Planner는 빠른 응답을 생성하고, 전역적인 정보를 사용하지 않기 위하여 반사적인 제어 방식에 의한 경로 생성 방식을 채택하였고, 제어기 부분은 비선형 posture feedback stabilizer로 설계하였다. 제안된 시스템은 단순한 형태의 제어 방식으로 완전한 자율적인 판단에 의한 장애물 회피와 목표 지점으로의 수렴 능력을 보여 준다. 본 시스템의 단순하면서도 효과적인 자율주행 능력은 반사제어 방식의 장점과 feedback 제어기의 증명된 안정성에서 기인한다. 시뮬레이션과 자체 구현한 차륜 구동 이동 로봇인 "MARI"로 실제 환경에서의 실험을 실시하여 제안된 제어기의 유효성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.439-440
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• 2015

유도가열은 석유, 가스 등의 연료를 사용하는 종래의 설비에 비해 에너지 효율이 높고 관리가 수월하며, 공해를 유발하지 않는 등의 많은 장점으로 인해 산업 분야에 다양하게 응용되어 사용하고 있다. 유도가열의 원리는 전자유도작용을 이용하여 와전류에 의한 손실과, 히스테리시스 손실에 의한 주울열이 발생하는데, 이렇게 발생된 열로 가열하는 방법이며 가열 속응성, 고효율, 친환경, 안정성의 장점을 갖는다. 그러나 공진형 유도가열 인버터 시스템은 환경의 변화나 피가열체의 부식 등의 이유로 공진주파수가 변하는 단점이 있다. 따라서 기존의 단점을 극복하기 위해 자동으로 공진점을 추종할 수 있는 알고리즘을 제안하였고, 기존의 복잡한 제어회로나 알고리즘을 극복하여 시스템의 간소화를 실현하였다.

• Journal of Korean Society of Transportation
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• v.33 no.4
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• pp.405-416
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• 2015

This paper developed a method analyze drivers' response characteristics using spectral analysis with car following data. Cross-correlation function and cross spectrum are produced by Fourier transform from speed fluctuations of leading vehicle and following vehicle during the designated time ${\tau}$. Based on the analysis data, a process to calculate the reaction time and stimulus-adaption index of following vehicle was developed and 170 cases of field data was applied. It was reported average of 0.654 and 2.091 seconds of stimulus-adaption index and reaction time respectively. In conclusion, the developed indexes might contribute to enhance vehicle control of autonomous vehicle more efficient and safer.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2901-2903
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• 2000

This thesis deals with study and implementation of Fuzzy controller with observer which can enhance the path-tracking performance of optically guided AGV(Automated Guided Vehicle). The AGV in this thesis is differential drive type and has front-side and rear-side optical sensors. which can identify the guiding path. This controller has excellent disturbance rejection and therefore is advantageous when it is instructed to follow straight paths. This fuzzy controller with observer enhances transient performance of the controller is demonstrated by simulation and is compared with that of individual loop controller

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.5
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• pp.609-617
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• 2013

This paper presents a near-minimum time path planning algorithm for autonomous driving. The problem of near-minimum time path planning is an optimization problem in which it is necessary to take into account not only the geometry of the circuit but also the dynamics of the vehicle. The path planning algorithm consists of a candidate path generation and a velocity optimization algorithm. The candidate path generation algorithm calculates the compromises between the shortest path and the path that allows the highest speeds to be achieved. The velocity optimization algorithm calculates the lap time of each candidate considering the vehicle driving performance and tire friction limit. By using the calculated path and velocity of each candidate, we calculate the lap times and search for a near-minimum time path. The proposed algorithm was evaluated via computer simulation using CarSim and Matlab/Simulink.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.1
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• pp.47-54
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• 2011

The remote control mobile robot is the robot accomplishing a task according to the orders giving by a user through departed communication system using a joystick. Basically, to supply a lot of information, as this type of robot uses visual information, the user can check the transmitted information by eyes and give orders to the robot. But the weak point of this type of robot is that it has a possibility to come into a collision with an obstacle not be seen to the user because of the communication delay occurring in a communication system and dead zone happening in visual information. To solve the problem, in this paper, we try to suggest a system applying a fuzzy control system to the robot to avoid collision with an obstacle by an immediate order of the user. The fuzzy control system has better performance than any other existing control methods in the change of noise and parameter. And it is more efficient than any other since it solves easy the complexity of the system analysis occurring because of the nonlinear feature of the mobile robot system. In this paper, we made experiments how the mobile robot controlled by the fuzzy control system avoids an obstacle, tracks the path and avoids the obstacle in the path, to prove the performance and to check the evaluation and the application possibility of the fuzzy control system.