• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.818-829
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• 2003

A cooperating control algorithm for two nonholonomic mobile robots is proposed. The task is composed of collision avoidance against obstacles and carrying a ladder. The front robot and the rear robot are called the leader and the follower, respectively. Each robot has a nonholonomic constraint so it cannot move in perpendicular directions. The environment is initially supposed to be unknown except target position. The torque that drives leader is determined by distance between the leader and the target position or the distance between it and the obstacles. The torque by target is attractive and the torque by obstacles is repulsive. The two mobile robots are supposed to be connected by link that can be expanded and contracted. The follower computes its torque using position and orientation information from the leader by communication. Simulation results show that the robots can drive to target position without colliding into the obstacles and maintain the distance in the allowable range.

• 동력기계공학회지
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• 제5권2호
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• pp.79-86
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• 2001

A method is presented for generating the path which significantly reduces residual vibration of the redundant, flexible robot manipulator in the presence of obstacles. The desired path is optimally designed so that the system completes the required move with minimum residual vibration, avoiding obstacles. The dynamic model and optimal path are effectively formulated and computed by using special moving coordinate, called VLCS, to represent the link flexibility. The path to be designed is developed by a combined Fourier series and polynomial function to satisfy both the convergence and boundary condition matching problems. The concept of correlation coefficients is used to select the minimum number of design variables. A planar three-link manipualtor is used to evaluate this method. Results show that residual vibration can be drastically reduced by selecting an appropriate path, in the presence of obstacles.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.1113-1116
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• 1999

For mobile robot, the navigation effectiveness can be improved by providing autonomy, but this autonomy requires the mobile robot to detect unknown obstacles and avoid collisions while moving it toward the target. This paper presents an effective method for autonomous navigation of the mobile robot in structured environments. This method uses ultrasonic sensor array to detect obstacles and utilizes force relationship between the obstacles and the target for avoiding collisions. Accuracy of sensory data produced by ultrasonic sensors is improved by employing error eliminating rapid ultrasonic firing (EERUF) technique. Navigation algorithm controlling both the velocity and steering simultaneously is developed, implemented to the mobile robot and tested on the floor filled with the cluttered obstacles. It is verified that from the results of the field tests the mobile robot can move at a maximum speed of 0.66 m/sec without any collisions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1040-1045
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• 1991

An approach to time-varying obstacle avoidance problem is pursued. The mathematical formulation of the problem is given in Cartesian space and in joint space. To deal with the time-varying obstacles, view-time is introduced. A view-time is the time interval viewing the time-varying obstacles to model equivalent stationary obstacles. For the analysis of the properties of the view-time, avoidability measure is defined as a measure of easiness for a robot to avoid obstacles. Based on the properties, a motion planning strategy to avoid time-varying obstacles is derived. An application of the strategy to the collision-free motion planning of two SCARA robots and the simulation on the application are given.

• 대한기계학회논문집B
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• 제29권12호
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• pp.1369-1376
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• 2005

Effective mixing gives strong advantageous impact on microfluidic applications since mixing is in general very slow process motivated by molecular diffusion transport only on the micro-scale. In this work, the mixing characteristics are analyzed in a Y-channel micromixer with obstacles. For the through analysis, our laboratory in-house unstructured grid CFD code is validated through solving a concentration transport in a uniform microchannel. The solutions well correspond to both exact solutions and those from MemCFD. Mixing in a Y-channel micromixer with obstacles is numerically investigated by the in-house code to search the optimal radius and layout of obstacles. From the simulations, the mixing efficiency appears to be proportional to the magnitude of the formation of lateral velocity component. It is also shown that the asymmetric layout and radius enlargement of obstacles greatly improves mixing efficiency.

• 융합보안논문지
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• 제17권2호
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• pp.81-88
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• 2017

암호화된 공간데이터베이스와 같은 최근의 여러 응용에서는 질의 기준이 최대근접객체가 되는 객체들을 찾는 역최대 근접질의가 자주 발생한다. 실세계의 검색공간에는 강, 호수 그리고 고속도로 등과 같은 다양한 장애물이 존재하며, 이러한 환경에서 검색성능을 높이기 위해서는 장애물을 고려한 검색거리 측도가 반드시 필요하다. 본 연구에서는 장애물이 존재하는 검색공간에서 역최대근접질의 처리를 최적화하기 위한 검색거리 측도들과 질의처리 알고리즘을 제시한다.

• International journal of advanced smart convergence
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• 제8권2호
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• pp.30-38
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• 2019

Recently, the spread of personal mobility has been rapidly increasing due to the development of environmentally friendly alternative transportation means. In addition, the level of battery technology is also rapidly developing, accelerating the popularization of personal mobility. Such personal mobility has convenience of location transfer, amusement, and high portability compared to other transportation devices. Most personal mobility, however, is made up of small wheels, which cannot overcome obstacles such as rugged roads or obstacles on the road. In this paper, to solve these problems, we tried to devise a device that can easily overcome obstacles by combining wheels with small moving means. The wheel size can be mounted on the front wheel of the small moving means in a protruding manner so that obstacles can be encountered before the front wheels and the safety and ride comfort of the running can be improved.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2003년도 ISIS 2003
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• pp.583-586
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• 2003

There are electric four-wheeled vehicles to assist elder people. Because of the vehicles'dynamic characteristic such as impossible to move abeam, it is difficult for these people who has little experience and has little knowledge to drive. Also to judge the future state of dynamic obstacles and to decide how to elude them safely are more difficult. We installed the predictive fuzzy controller(evaluates the future states which several kinds of operation candidates were done and chooses the best one) that modeled humans'algorithms in the system. Human predicts the future states of dynamic obstacles and chooses an operation(wait, steer, go back, etc) to elude safely. To elude dynamic obstacles flexibly, we added expert's knowledge for safe driving to this controller. In this paper, we propose the intelligent soft driving system by the controller that can elude dynamic obstacles safely, and we confirm the effectiveness by a simulation.

• 한국관개배수논문집
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• 제6권2호
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• pp.19-27
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• 1999

In this paper, the variation of flow characteristics by obstacles in urban streams is studied with laboratory experiments. Experiments to measure the depths and velocities affected by rectangular shape obstacles which are general in the field were perform

• Journal of Information Technology Applications and Management
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• 제20권2호
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• pp.211-230
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• 2013

This paper presents how users and operators of smart work centers think about benefits from and obstacles to smart work centers. First, this paper reviewed the previous literature to summarize benefits and obstacles. Then, in-depth interviews with users and operators were conducted to identify the current issues in smart work centers. Finally, a survey method was used to collect opinions of more users and managers and the co-orientation model was employed to analyze diverse patterns. This study found that users and operators mostly agree with the benefits from the smart work centers. However, they expressed various forms of disagreement over obstacles and ways to overcome the obstacles.