Author name cluster

Sun-Gi Hong

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

7 papers

1 author row

IROS Conference 2005 Conference Paper

Real-time audio-visual localization of user using microphone array and vision camera

Changkyu Choi
Donggeon Kong
Sujin Lee
Kiyoung Park
Sun-Gi Hong
Hyoung-Ki Lee
Seokwon Bang
Yongbeom Lee

In home environments, demands for a robot to serve a user are on the increase, such as cleaning rooms, bringing something to the user, and so on. To achieve these tasks, it is essential for developing a natural way of human-robot interaction (HRI). One of the most natural ways is that the robot approaches the user to do some tasks after recognizing the user's call and localizing its position. In this case, user localization becomes a key technology. In this paper, we propose a novel audio visual user localization system. It consists of a microphone array with eight sensors and a video camera. Estimating calling direction is achieved by the spectral subtraction of the spatial spectra. In particular, a novel beam forming method is proposed to suppress the nonstationary audio noises where they always occur in a real world. Furthermore, a robust method for face detection is proposed to double check the user based on an Adaboost classifier. It is improved to reduce the false alarms remarkably through a new postprocessing on face candidates. Successful results in a real home environment show its efficacy and feasibility. The implementation issues, limitations, and their possible solutions are also discussed.

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IROS Conference 2002 Conference Paper

Evolutionary design of fuzzy system for various problems including vision based mobile robot control

Min-Soeng Kim
Sun-Gi Hong
Ju-Jang Lee

In this paper, a new evolutionary scheme for designing fuzzy logic system is proposed. We have developed a new fitness function for optimizing membership functions of antecedent parts of FLS. The proposed fitness function considers not only mean squared error, but also calculates some penalty based on the overlapping degree of adjacent membership functions for the same input. Consequent parts of the FLS are calculated using pseudo-inverse method. To show the effectiveness of the proposed algorithm, we have applied the proposed algorithm to various problems: Iris classification problem, Mackay-Glass time-series prediction problem and vision-based mobile robot control problem. It has been proven that, without much modification, the proposed algorithm can be used in various problem fields efficiently.

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IROS Conference 1999 Conference Paper

An active contour model using image flow for tracking a moving object

Won Kim
Sun-Gi Hong
Ju-Jang Lee

An active contour model was developed as a useful segmenting and tracking tool for rigid or nonrigid objects. Snake, one of the active contour models (ACMs), is designed on the basis of Snake energies. Segmenting and tracking can be executed successfully by the process of energy minimization. The ability to contract is a important process for segmenting objects from images, but the contraction forces of Kass' Snake are dependent on the object's form. In this research, new contraction energy, independent of the object's form, is proposed for the segmentation. Kass' Snake can be applied to the case of small changes between two images because its solutions can be obtained from the basis of variational approach. Furthermore considering the case that the motion is too large to apply image flow energy to tracking. A jump mode was proposed for solving the problem.

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IROS Conference 1999 Conference Paper

Generating artificial force for feedback control of teleoperated mobile robots

Sun-Gi Hong
Ju-Jang Lee
Seungho Kim

One of the most important issues in the teleoperation is to provide the sense of telepresence so as to conduct the task more reliably. In particular, teleoperated mobile robots need to have some kind of backup system when the operator is blind to the remote situation owing to failure of the vision system. In Hong S-G et al. (see Mechatronics), the idea of artificial force reflection was proposed to enhance the reliability of operation when the mobile robot travels over plain ground. We extend these results to help the teleoperator even when the robot climbs stairs. The extended artificial force reflection method has two modes: traveling on plain ground and climbing stairs. When traveling over plain ground, the force information is artificially generated using range data from the environment while generating the impulse force when climbing stairs. To verify the validity of our algorithm, we develop a simulator which consists of a joystick and visual display system. Through experiments using this system, we confirm the validity and effectiveness of our new artificial force reflection in teleoperated mobile robots.

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IROS Conference 1999 Conference Paper

Online fuzzy Q-learning with extended rule and interpolation technique

Min-Soeng Kim
Sun-Gi Hong
Ju-Jang Lee

Q-learning is a kind of reinforcement learning where the agent solves the given task based on rewards received from the environment. Most research done in the field of reinforcement learning has focused on discrete domains. But the environment with which the agent must interact is continuous. Thus a method that is able to make Q-learning applicable to the continuous problem domain is needed. In the paper, the basic fuzzy rule is extended so that it can incorporate Q-learning. The interpolation technique which is widely used in memory-based learning is adopted to represent the appropriate Q-value for current state and action pair. The resulting structure based on the fuzzy inference system has the capability of solving the continuous state and action problem in Q-learning and generating fuzzy rules via interacting with the environment without a priori knowledge about the environment. The effectiveness of the proposed structure is shown through simulation on cart-pole system.

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ICRA Conference 1996 Conference Paper

Local motion planner for nonholonomic mobile robots in the presence of the unknown obstacles

Sun-Gi Hong
Sung-Woo Kim
Kang-Bark Park
Ju-Jang Lee

This paper deals with the problem of motion planning for a unicycle-like robot. A simple local planner for unicycle model, based on an approximation of the desired configuration generated by local holonomic planner that ignores motion constraints, is presented. To guarantee a collision avoidance, we propose an inequality constraint, based on the motion analysis with the constant control input and time interval. Consequently, we formulate the problem as a constrained optimization problem, and a feedback scheme based on local sensor information is established by simply solving this problem. Through simulations, we confirm the validity and effectiveness of our algorithm.

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IROS Conference 1995 Conference Paper

Dynamical path-planning algorithm of a mobile robot using chaotic neuron model

Changkyu Choi
Sun-Gi Hong
Jin-Ho Shin
Il-Kwon Jeong
Ju-Jang Lee

This paper describes a dynamical local path-planning algorithm of an autonomous mobile robot available for stationary obstacle avoidance using nonlinear friction. Dynamical path-planning algorithm is considered to accommodate the mobile robot to the dynamic situation of the path-planning nature. Together with the previous virtual force field method, the path of the mobile robot is a solution of a path-planning equation. Local minima problems in stationary environments are solved by introducing nonlinear friction into the chaotic neuron. Because of the nonlinear friction, the proposed path-planner reveals chaotic dynamics in some parameter regions. This new path-planner is feasible to guide, in real-time, the mobile robot to avoid stationary obstacles and to reach the goal. Computer simulations are presented to show the effectiveness of the proposed algorithm.

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