• 대한산업공학회지
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• 제28권1호
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• pp.25-35
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• 2002

This paper presents a heuristic algorithm that a mobile robot avoids obstacles using optical flow. Using optical flow, the mobile robot can easily avoid static obstacles without a prior position information as well as moving obstacles with unknown trajectories. The mobile robot in this paper is able to recognize the locations or routes of obstacles, which can be detected by obtaining 2-dimensional optical flow information from a CCD camera. It predicts the possibilities of crash with obstacles based on the comparison between planned routes and the obstacle routes. Then it modifies its driving route if necessary. Driving acceleration and angular velocity of mobile robot are applied as controlling variables of avoidance. The corresponding simulation test is performed to verify the effectiveness of these factors. The results of simulation show that the mobile robot can reach the goal with avoiding obstacles which have variable routes and speed.

• 한국자동차공학회논문집
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• 제22권3호
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• pp.241-249
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• 2014

This paper presents a path planning algorithm of an autonomous vehicle (ADAM III) for collision avoidance in the presence of multiple obstacles. Under the requirements that a low-cost GPS is used and its computation should be completed with a sampling time of sub-second, heading angle estimation is proposed to improve performance degradation of its measurement and a hierarchical structure for path planning is used. Once it is decided that obstacle avoidance is necessary, the path planning consists in three steps: waypoint generation, trajectory candidate generation, and trajectory selection. While the waypoints and the corresponding trajectory candidates are generated based on position of obstacles, the final desired trajectory is determined with considerations of kinematic constraints as well as an optimal condition in a term of lateral deviation. Finally the proposed algorithm was validated experimentally through field tests and its demonstration was performed in Autonomous Vehicle Competition (AVC) 2013.

• 전기학회논문지
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• 제64권7호
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• pp.1081-1087
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• 2015

Recently, the researches of aerial drones are actively executed in various areas, the researches of surface drones and underwater drones are also executed in marine areas. In case of surface drones, they essentially utilize acoustic information by the sonar and consequently have the local information in the obstacle avoidance as the sonar has the limitations due to the beam width and detection range. In order to overcome this, more global method that utilizes optical images by the camera is required. Related to this, the aerial drone with the camera is desirable as the obstacle detection of the surface drone with the camera is impossible in case of the existence of clutters. However, the dynamic-floating aerial drone is not desirable for the long-term operation as its power consumption is high. To solve this problem, a collaborative obstacle avoidance method based on the acoustic information by the sonar of the surface drone and the optical image by the camera of the static-floating aerial drone is proposed. To verify the performance of the proposed method, the collaborative obstacle avoidances of a MSD(Micro Surface Drone) with an OAS(Obstacle Avoidance Sonar) and a BMAD(Balloon-based Micro Aerial Drone) with a camera are executed. The test results show the possibility of real applications and the need for additional studies.

• 한국철도학회논문집
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• 제20권2호
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• pp.173-181
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• 2017

장애물제거기는 선로 내 장애물에 의한 충돌사고 발생 시 장애물을 선로 밖으로 밀어내거나 에너지흡수부재를 통해 충돌에너지를 흡수하여 열차 탈선을 방지하고 충돌사고에 의한 피해를 최소화하기 위한 장치이다. 본 연구에서는 인장형 에너지흡수부재와 4절 링크를 이용하여 장애물제거기의 작동 메커니즘을 구성하여 장애물제거기를 설계하였다. 또한 EN 15227에서 요구하는 정적강도 및 에너지흡수조건을 확인하기 위한 성능검증시험 방법을 고안한 뒤 유한요소해석 및 UTM (Universal Test Machine)을 이용한 성능검증시험을 수행하였다. 본 연구를 통해 EN 15227의 요구조건을 만족하는 장애물제거기를 개발하였으며, 제안된 장애물제거기의 설계 및 검증 절차에 따라 붕괴하중의 조절이 가능하며 이를 실험을 통해 검증할 수 있는 방법을 제안하였다.

• 한국지능시스템학회논문지
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• 제15권4호
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• pp.498-504
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• 2005

본 논문에서는 퍼지 로직을 이용한 수중 로봇의 충돌 회피를 제안하였다. VFF(Virtual Force Field) 방법은 이동 로봇 분야에서 널리 사용하고 있는 충돌 회피 알고리즘이다. 본 논문에서는 이를 수중 로봇의 자율 항해를 위한 형태로 변형시킨 Modified Virtual Force Field(MVFF)를 제시하였다. 보다 정교한 알고리즘을 위해서 퍼지 로직을 이용한 MVFF를 구성하였고, 이를 수중 로봇의 경로 유지와 충돌 회피에 적용하였다 퍼지 로직은 수중 로봇의 자율 항해 동안 직면하게 되는 다양한 상황들을 다루었다. 제안한 충돌 회피 알고리즘은 다수개의 고정 장애물에 대해서 좋은 성능을 제시하였다. 시뮬레이션 결과를 통해 제안된 방법이 수중 로봇의 충돌 회피에 효과적으로 적용될 수 있음을 보였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.319-322
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• 1995

This paper addresses that through the use of Fuzzy Logic Control, a reactiv behavior (e.g. avoiding obstacles on the way) are smoothly blended into one sequence of control action. In this classical problem, the aim is to guide a mobile robot along its path to avoid any static obstacles in front of it. This controller presented here uses three sub-controllers. This fuzzy controller was apply to a miniature mobile robot. This robot follows a left wall, maintining a minimum distance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2447-2449
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• 2004

This paper presents the predicted polar mapping that is to improve the efficiency of an unexpected moving obstacle detecting system. When the movement of the robot per a step becomes a bit large then static objects or background are detected as moving objects. Thus, the velocity of the robot becomes so slow. Therefore, to enlarge the movement of the robot, we propose the predicted polar mapping that predicts the polar mapped image after robot moves to be admissible. In order to verify experimentally our proposed procedure, we make several comparative tests in the corridor.

• 한국정밀공학회지
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• 제18권10호
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• pp.116-126
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• 2001

This paper suggests a numerical method to find optimal geometric path and minimum-time motion for a spatial 6-link manipulator arm (PUMA 560 type). To find a minimum-time motion, the optimal geometric paths minimizing 2 different dynamic performance indices are searched first, and the minimum-time motions are searched on these optimal paths. In the algorithm to find optimal geometric paths, the objective functions (performance indices) are selected to minimize joint velocities, actuator forces or the combinations of them as well as to avoid one static obstacle. In the minimum-time algorithm the traveling time is expressed by the power series including 21 terms. The coefficients of the series are obtained using nonlinear programming to minimize the total traveling time subject to the constraints of velocity-dependent actuator forces.

• 로봇학회논문지
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• 제2권2호
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• pp.183-190
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• 2007

The most important thing for navigation of a mobile robot is to find the most suitable path and avoid the obstacles in the static and dynamic environment. This paper presents a method to search the optimal path in start space extended to time domain with considering a velocity and a direction of moving obstacles. A modified version of $A^*$ algorithm has been applied for path planning in this work and proposed a method of path search to avoid a collision with moving obstacle in space-tim domain with a velocity and an orientation of obstacles. The velocity and the direction for moving obstacle are assumed as linear form. The simulation result shows that a mobile robot navigates safely among moving obstacles of constant linear velocity. This work can be applied for not only a moving robot but also a legged humanoid robot and all fields where the path planning is required.

• The Journal of Korean Physical Therapy
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• 제21권4호
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• pp.51-56
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• 2009

Purpose: This study examined the difference in the static balance ability according to the visual cues and postural tasks in normal subjects. Methods: Thirty participants (12 male, 18 female; mean age $24.63\pm1.43$ years) stood barefoot on a force platform in a one-legged stance, tandem Romberg stance and tandem Romberg with neck extension stance with a visual cue open and closes. The static balance was assessed by the center of pressure (CoP), surface electromyography root mean square (RMS) of the leg muscles according to the stance position. Results: In the CoP tests, the difference in the unit path length and circumference area was affected by the visual cue according to the stance posture (p<0.01). In the RMS tests, the difference in the tibialis anterior and medial gastrocnemius muscle was affected by visual cue in accordance with the stance posture (p<0.01). Conclusion: The visual cue and postural task affect the balance ability in normal subjects. Therefore, this study provides clinical evidence that the balance and postural control can be improved. Therapeutic intervention, such as an obstacle course, and a lower leg muscle performance program with a change in the base of support can affect the balance and postural control.