• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.692-700
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• 2012

The WiMedia Alliance has specified a Distributed Medium Access Control (D-MAC) protocol based on UWB for high speed wireless home networks and Wireless USB. In this paper, firstly, the fair SoQ-based Distributed Reservation Protocol (DRP) for D-MAC is analyzed. And a novel SoQ-based relay transmission protocol is proposed to overcome DRP conflicts fast. In the proposed protocol, each device executes the Satisfaction of QoS (SoQ) time slot allocation algorithm independently. And, in order to give the loser device due to DRP conflicts another chance to maintain QoS resources, the proposed relay transmission protocol helps the device reserve another indirect link maintaining the required QoS resources via a relay node.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.10
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• pp.3160-3172
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• 1996

A search algorithm for the collision free, time optimal transport path of overhead cranes has been proposed in this paper. The map for the working environment of overhead cranes was constructed in the form of three dimensional grid. The obstacle occupied region and unoccupied region of the map has been represented using the octree model. The best-first search method with a suitable estimation function was applied to select the knot points on the collision free transport path to the octree model. The optimization technique, minimizing the travel time required for transporting objects to the goal while subjected to the dynamic constraints of the crane system, was developed to find the smooth time optimal path in the form of cubic spline functions which interpolate the selected knot points. Several simulation results showed that the selected estimation function worked effectively insearching the knot points on the collision free transport path and that the resulting transport path was time optimal path while satisfying the dynamic constraints of the crane system.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.10
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• pp.936-940
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• 2013

As the ageing population grows around the world, the demand for electric wheelchairs, an important mobility assistance device for the disabled and elderly, is gradually increasing. Therefore, a number of studies related to intelligent wheelchairs are actively underway to improve safety and comfort for wheelchair users. However, previous collision avoidance studies for intelligent wheelchairs have concentrated on collision avoidance methods with the shortest distance and by only changing either velocity or heading angle, rather than considering the forces exerted on the user. If a collision avoidance algorithm that does not consider these forces is applied to an intelligent wheelchair, there is a possibility of an accident due to falling as wheelchair users are generally disabled and elderly people. In this paper, we propose a collision avoidance algorithm which minimizes the forces exerted on a wheelchair user by minimizing the variation of the wheelchair's velocity and heading angle when the sizes, positions, velocities, and heading angles of a wheelchair and a moving obstacle are known.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.6
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• pp.586-595
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• 2022

In this paper, we propose a formation control algorithm for multi-USVs according to COLREGs. First, we applied the Dynamic Window Approach algorithm that can reflect the kinematic characteristics for the path movement of USVs. Then, we propose a virtual structure-based virtual leader-follower method that applies the advantages of leader-follower and virtual structure methods among conventional formation control algorithms for stability. Next, we proposed a collision avoidance algorithm according to all COLREGs when encountering an opposing ship by adding COLREGs situational conditions to the virtual leader, and finally confirmed the feasibility of the proposed method through simulation.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.51-60
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• 2009

In radio frequency identification(RFID) systems, when an RFID reader uses the same or adjacent frequency with neighbor readers, the interference between the readers may occur, which causes the reader collision and errors in tag recognition. In the previous study on RFID reader anti-collision, the techniques based on Frequency Division Mutiplex(FDM) or Time Division Multiplex(TDM) are proposed. However in these paper, the problem on the condition of RFID reader-to-reader interference considering the distance between interfering readers, frequency and operating time is not define exactly. In this paper, the interference effect is analyzed through RFID reader interference model considering the TDM and FDM, and the optimization problem is defined. To solve this, genetic-resource allocation technique is proposed. Therefore the optimal resource allocation applied RFID environment faithfully is accomplished.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.4
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• pp.392-397
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• 2014

Recently, there are many researches on active safety system of intelligent vehicle. To reduce the probability of collision caused by driver's inattention and mistakes, the active safety system gives warning or controls the vehicle toward avoiding collision. For the purpose, it is necessary to recognize and analyze circumstances around. In this paper, we will treat the problem about collision risk assessment. In general, it is difficult to calculate the collision risk before it happens. To consider the uncertainty of the situation, Monte Carlo simulation can be employed. However it takes long computation time and is not suitable for practice. In this paper, we apply neural networks to solve this problem. It efficiently computes the unseen data by training the results of Monte Carlo simulation. Furthermore, we propose the features affects the performance of the assessment. The proposed algorithm is verified by applications in various crash scenarios.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.4
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• pp.451-456
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• 2009

In this paper, a virtual force is generated and fed back to the operator to make the teleoperation more reliable, which reflects the relationship between a slave robot and an uncertain remote environment as a form of an impedance. In general, for the teleoperation, the teleoperated mobile robot takes pictures of the remote environment and sends the visual information back to the operator over the Internet. Because of the limitations of communication bandwidth and narrow view-angles of camera, it is not possible to watch certain regions, for examples, the shadow and curved areas. To overcome this problem, a virtual force is generated according to both the distance between the obstacle and the robot and the approaching velocity of the obstacle w.r.t the collision vector based on the ultrasonic sensor data. This virtual force is transferred back to the master (two degrees of freedom joystick) over the Internet to enable a human operator to estimate the position of obstacle at the remote site. By holding this master, in spite of limited visual information, the operator can feel the spatial sense against the remote environment. It is demonstrated by experiments that this collision vector based haptic reflection improves the performance of teleoperated mobile robot significantly.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.7
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• pp.1302-1308
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• 2007

In this paper, a real-time collision avoidance algorithm is proposed for experimental Autonomous Vehicle(XAV). To ensure real-time implementation, a virtual potential field is calculated in one dimensional space. The attractive force is generated by the steering command either transmitted in the remote control station or calculated in the Autonomous Navigation System(ANS) of the XAV. The repulsive force is generated by obstacle information obtained from Laser Range Finder(LRF) mounted on the XAV. Using these attractive and repulsive forces, modified steering, velocity and emergency stop commands are created to avoid obstacles and follow a planned path. The suggested algorithm is inserted as one component in the XAV system. Through various real experiments and technical demonstration using the XAV, the usefulness and practicality of the proposed algorithm are verified.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.7
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• pp.700-705
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• 2006

This paper proposes a collision avoidance algorithm for two mobile robots with independent goals in a same workspace. Using skeleton map, an environment is presented as a graph consisting of nodes and arcs. Robots generate the shortest set of paths using the combination of objective functions of the two robots. Path for collision avoidance of a robot can be selected among three class; the shortest path, detour, paths with a waiting time at safety points around crossing points. Simulation results are presented to verify the efficiency of the proposed algorithms.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.105-106
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• 2015

무인 자율 자동차는 사람이 차량 제어에 개입할 수 있는 일반적인 '무인 자동차'와는 달리 센서, 메라와 같은 '장애물 인식장치'와 GPS모듈 과 같은 '자동 항법 장치'를 기반으로 조향, 변속, 가속, 브레이크를 도로환경에 맞춰 스스로 제어해 목적지까지 주행할 수 있는 차량을 의미한다. 따라서 무인 자율 주행 자동차에는 차량제어기술, 차선인식기술, 충돌 회피 기술 등이 필요 하며 이를 위해 각종 센서뿐만 아니라 센서 네트워크, 컴퓨터비전, 인공지능 등의 다양한 기술들이 접목되어야 한다. 본 논문은 소형 무인자동차의 제작을 통한 알고리즘과 그 평가에 대해서 나타낼 것이다.