• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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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.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.113-116
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• 2002

In this paper, we propose the sound-mapping algorithm of the detected obstacle by ultrasonic sensors. We apply this algorithm to a Obstacle alarm for the visually impaired. In our system, we acquire obstacles information using ultrasonic sensors, and transform two-dimensional and distance information into sound-imaging information and vibrator with azimuth (direction) and distance. We implement this system with ultrasonic sensors to more effective expression of the obstacle information. The distance of an obstacle can be expressed by sound pressure level, and azimuth of the obstacles can be expressed by inter-aural time difference (ITD) and inter-aural level difference (ILD) that are two important cues in a binaural system. These are the principal cues for sound localization, to detect sound source. In this system, the obstacle is substituted with a sound source. The visually impaired receive sound information of obstacles by headphone.

• Journal of Biosystems Engineering
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• v.25 no.2
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• pp.141-150
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• 2000

This study was carried out to de develop a control strategy of a fruit harvesting redundant robot. The method of generating a safe trajectory, which avoids collisions with obstracles such as branches or immature fruits, in the 3D(3-dimension) space using artificial potential field technique and virtual plane concept was proposed. Also, the method of setting reference velocity vectors to follow the trajectory and to avoid obstacles in the 3D space was proposed. Developed methods were verified with computer simulations and with actual robot tests. Fro the actual robot tests, a machine vision system was used for detecting fruits and obstacles, Results showed that developed control method could reduce the occurrences of the robot manipulator located in the possible collision distance. with 10 virtual obstacles generated randomly in the 3 D space, maximum rates of the occurrences of the robot manipulator located in the possible collision distance, 0.03 m, from the obstacles were 8 % with 5 degree of freedom (DOF), 8 % with 6-DOF, and 4% with 7-DOF, respectively.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.9-21
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• 1998

This paper a new solution approach to moving obstacle avoidance problem of a mobile robot. A new concept avoidability measure (AVM) is defined to describe the state of a pair of a robot and an obstacle regarding the collision between them. As an AVM, virtual distance function (VDF), is derived as a function of the distance from the obstacle to the robot and outward speed of the obstacle relative to the robot. By keeping the virtual distance above some positive limit value, the robot avoids the obstacle. In terms of the VDF ,an artificial potential field is constructed to repel the robot away from the obstacle and to attract the robot toward a goal location. At every sampling time, the artificial potential field is updated and the force driving the robot is derived from the gradient of the artificial potential field. The suggested algorithm drives the robot to avoid moving obstacles in real time. Since the algorithm considers the mobility of the obstacle as well as the distance, it is effective for moving obstacle avoidance. Some simulation studies show the effectiveness of the proposed approach.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.500-503
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• 2003

The navigation problem of robot is one of the main themes to deal with conficts or interferences between obstacles and the robot itself In this case, while the robot avoids obstacles on the space, the passage route should be determined efficiently. In order to solve problems above, we have come up with the distance field space medel (DFM) and then, under known environment, we have presented the distance field A algorithm for passage route path search. In this research, the method of performing the 3-dimensional passage route path search of robot under unknown environment is proposed. It is shown that the authors can build the distance search model the does not need space division by taking into account of sensor information to a distance field space model, and constructing this information as virtual obstacle information.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.326-334
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• 2022

This study aimed to explore science teachers' perceptions of obstacles that have affected their teaching during the COVID-19 pandemic. The sample comprised 204 science teachers in public schools within a Western district of Saudi Arabia. Results revealed that these teachers experienced obstacles across six areas: administration, students, teaching methods, assessment, technology, and learning aids. The study also explored teachers' perceptions of their current experience and offers suggestions for dealing with the identified obstacles.

• Journal of the Korean Institute of Landscape Architecture
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• v.33 no.2 s.109
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• pp.83-91
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• 2005

The purpose of this study is to analyze the arrangement of parks, in whole city level by using park's effective distance and to find the accessibility obstacles in case of using parks, in boundary of each parks' effective distance, so that to show how to improve communities' usage of city parks. The 8 cities in Gyeonggi-do and analysed the effective distance of parks. To find the accessibility obstacles in the boundary of parks' effective distance, 1) we choose 18 sample parks and extract obstacles - wide road, rail road, river- in interior and verify it by field survey and asking the park user's residents directly. The main findings of this study can be summarized as follows: First, Ansan city and Goyang city are only satisfied with the minimal city parks size standard, so that the rest 6 cities are lack of quantities which residents can use. The result of analyzing effective distance in whole city level, parks are mainly designated in new-town, so that most cities which have old-towns have very poor park systems to use. Because Ansan city is new-planned city, it is very effective arrangement in park systems exceptionally. Second, $96.2\%$ of park users' are living in the area which was easy to gain access not intercepted by wide road, rail road or river. Third, therefore at the stage of planning park, effective distance and resident's accessibility as well as park's supply quantitatively are needed to be considered. In addition, selection of location and elevation of resident's safety and accessibility through making a plan must be reflected. In the low accessibility area, the program to improve park's accessibility and amenity - like making small park or pocket park, linking parks with resident-friendly road etc.- has to be investigated.

• Journal of information and communication convergence engineering
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• v.19 no.3
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• pp.161-165
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• 2021

Since the first commercialization of beacon-based services in 2011, various services have been provided to improve Bluetooth performance, and research has been conducted to accurately recognize user locations using beacons. The various measurement methods of indoor positioning systems (IPS) include methods using receiver signal strength indicator (RSSI) the strength of which varies greatly in accuracy depending on whether there are obstacles such as cement walls or doors. In this paper, we present a method to provide accurate positioning services even in the presence of obstacles in indoor spaces. To this end, we connect the HM-10 module supporting the beacon with Arduino Uno, to place beacons in three directions in real-world indoor space, and derive an optimal trilateration equation. Based on the derivation, we select the optimal expression for calculating the distance between the beacon and the moving station and use it to verify the coordinate determination for the moving station.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.5 no.4
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• pp.316-321
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• 2005

We designed and implemented fish robots for various purposes such as autonomous navigation, maneuverability control, posture balancing and improvement of quick turns in a tank of 120 X 120 X 180cm size. Typically, fish robots have 30-50 X 15-25 X 10-20cm dimensions; length, width and height, respectively. It is essential to have the ability of quick and smooth turning to avoid collision with obstacles or walls of the water pool at a close distance. Infrared distance sensors are used to detect obstacles, magneto-resistive sensors are used to read direction information, and a two-axis accelerometer is mounted to compensate output of direction sensors. Because of the swing action of its head due to the tail fin movement, the outputs of an infrared distance sensor contain a huge amount of noise around true distances. With the information from accelerometers and e-compass, much improved distance data can be obtained by fuzzy logic based estimation. Successful swimming and smooth turns without collision demonstrated the effectiveness of the distance estimation.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.2
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• pp.65-71
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• 2018

In order to make the underwater vehicle carry out the mission in a submarine environment, it is needed to plan a safe and efficient route to a given destination and prevent the autonomous submersible from colliding with obstacles while moving along the planned route. The function of collision avoidance makes the travel distance of the autonomous submersible longer. Moreover, it should move slowly near to obstacles against their moving disturbance. As a result, this invokes the degradation of the navigation efficiency in the process of collision avoidance. The side effect of the collision avoidance is not ignorable in the case of high congested environments such as the coast with many obstacles. In this paper, we suggest a path planning method which provides the route with minimum travel time considering collision avoidance in congested environment. For the purpose, we define environmental congestion map related to geometric information and obstacles. And we propose a method to consider the moving cost in the RRT scheme that provides the existing minimum distance path. We verified that the efficiency of our algorithm with simulation experiments.