• Journal of Institute of Control, Robotics and Systems
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• v.9 no.8
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• pp.585-591
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• 2003

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.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.658-662
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• 1991

In this paper, a real-time obstacle avoidance for mobile robot based on the readings of the ultrasonic sensors is presented. The twenty eight ultrasonic sensors are arranged in ring and controlled by microprocessor. The readings of the ultrasonic sensor is converted into the virtual forces called repulsive forces, which are the elastic and damping forces. Then, the direction and speed of mobile robot in the cluttered environment are determined by the virtual forces. The effectiveness of the proposed method is verified from a series of simulation studies.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.1
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• pp.7-18
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• 2001

In this paper, we present a new method to generate obstacle-free path by using conformal mapping, when avatar navigates in virtual environment. First, we show that the proposed method generates a path to keep away from a circular obstacle. Then, we show that the method can be extended to an elliptical obstacle and multiple obstacles. For real applications, we combine the proposed local method with a global navigation method using sub-target to generate a global obstacle-free path by which avatar navigates naturally in virtual environment.

• The Journal of Korea Robotics Society
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• v.5 no.2
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• pp.127-134
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• 2010

In this paper, a hybrid semi-3D path planning algorithm combining Virtual Tangential Vector(VTV) and fuzzy control is proposed. 3D dynamic environmental factors are reflected to the 2D path planning model, VTV. As a result, the robot can control direction from 2D path planning algorithm VTV and speed as well depending on the fuzzy inputs such as the distance between the robot and obstacle, roughness and slope. Performances and feasibilities of the suggested method are demonstrated by using Matlab simulations. Simulation results show that fuzzy rules and obstacle avoidance methods are working properly toward virtual 3D environments. The proposed hybrid semi-3D path planning is expected to be well applicable to a real life environment, considering its simplicity and realistic nature of the dynamic factors included.

• Journal of the Korea Society of Computer and Information
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• v.14 no.11
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• pp.31-40
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• 2009

The most common cleaning methods of cleaning robot can be divided into two categories: the random and the boustrophedon method. A cleaning robot using the random method moves straight until it bumps into an obstacle. If it collides with an obstacle, the cleaning robot turns a specific angle and continues moving straight. Therefore, the random method often tends to clean the already clean area repeatedly. In addition, it takes a long time to complete cleaning. A cleaning robot using the boustrophedon method moves straight until it collides with an obstacle. If it meets an obstacle, the cleaning robot moves to the next uncleaned space through turning and moving ahead. when resuming cleaning from the new region, a cleaning robot moves in the direction opposite to the direction of the previous cleaning. Because the boustrophedon method cleans a cleaning space more densely, its performance is excellent in an obstacle-free space or a small space. However, In a space with obstacles or a complex structure, it takes a long time to complete the cleaning work. Cleaning should be systematically approached with a good understanding of the work area. The virtual map-based cleaning robot proposed in this paper cleaned a work space efficiently. The efficiency of the proposed method was measured through simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.5
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• pp.471-478
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• 2011

This UGV (Unmanned Ground Vehicle) is not only widely used in various practical applications but is also currently being researched in many disciplines. In particular, obstacle avoidance is considered one of the most important technologies in the navigation of an unmanned vehicle. In this paper, we introduce a simple algorithm for path planning in order to reach a destination while avoiding a polygonal-shaped static obstacle. To effectively avoid such an obstacle, a path planned near the obstacle is much shorter than a path planned far from the obstacle, on the condition that both paths guarantee that the robot will not collide with the obstacle. So, to generate a path near the obstacle, we have developed an algorithm that combines an edge detection method and a limit-cycle navigation method. The edge detection method, based on Hough Transform and IR sensors, finds an obstacle's edge, and the limit-cycle navigation method generates a path that is smooth enough to reach a detected obstacle's edge. And we proposed novel algorithm to solve local minima using the virtual wall in the local vision. Finally, we verify performances of the proposed algorithm through simulations and experiments.

• Journal of the Korea Society of Computer and Information
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• v.27 no.11
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• pp.81-87
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• 2022

In this paper, we propose diffraction-based sound control method to improve sound immersion in a virtual environment. The proposed technique can express the wave and flow of sound in a physical environment and a pattern similar to diffraction in real-time. Our approach determines whether there is an obstacle from the location of the sound source and then calculates the position of the new sound reflected and diffracted by the obstacle. Based on ray tracing, it determines whether or not it collides with an obstacle, and predicts the sound level of the agent behind the obstacle by using the vector reflected and refraction by the collision. In this process, the sound attenuation according to the distance/material is modeled by attenuating the size of the sound according to the number of reflected/refracted rays. As a result, the diffraction pattern expressed in the physics-based approach was expressed in real time, and it shows that the diffraction pattern also changes as the position of the obstacle is changed, thereby showing the result of naturally spreading the size of the sound. The proposed method restores the diffusion and diffraction characteristics of sound expressed in real life almost similarly.

• 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 Broadcast Engineering
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• v.27 no.5
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• pp.629-637
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• 2022

This study is an experiment on the use of RDW(Redirected Walking) technology, which helps users to hardly feel the difference of user movement in the limited physical space and the extended virtual space when the user moves while wearing the HMD in the real world. The RDW function installed in 3D space realization software such as Unity3D is used to induce the user's redirection by slightly distorting the virtual space according to the user's point of view. However, if the RDW distortion rate is used excessively, dissonance is highly likely to occur. In particular, it is easy to make errors that cause cybersickness of users. It is important to obtain the RDW data value in the virtual environment so that the user does not feel fatigue and cybersickness even after wearing the HMD for a long time. In this experiment, it was tested whether the user's RDW was safely implemented, and item and obstacle arrangement data were obtained through this experiment. The RDW data obtained as a result of the experiment were used for item placement and obstacle placement in the virtual space.

• Journal of Drive and Control
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• v.19 no.4
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• pp.110-116
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• 2022

Recently, various studies have been conducted to apply deep learning and AI to various fields of autonomous driving, such as recognition, sensor processing, decision-making, and control. This paper proposes a controller applicable to path following, static obstacle avoidance, and pedestrian avoidance situations by utilizing reinforcement learning in autonomous vehicles. For repetitive driving simulation, a reinforcement learning environment was constructed using virtual environments. After learning path following scenarios, we compared control performance with Pure-Pursuit controllers and Stanley controllers, which are widely used due to their good performance and simplicity. Based on the test case of the KNCAP test and assessment protocol, autonomous emergency steering scenarios and autonomous emergency braking scenarios were created and used for learning. Experimental results from zero collisions demonstrated that the reinforcement learning controller was successful in the stationary obstacle avoidance scenario and pedestrian collision scenario under a given condition.