C.K. Woo

Korea Advanced Institute of Science and Technology, Daiden, Daejeon, South Korea

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Publications (6)3.24 Total impact

  • H.D. Choi · C.K. Woo · S. Yoon · S. Kim · Y.K. Kwak
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    ABSTRACT: This paper proposes a traction control algorithm which can be independently implemented to each wheel without extra sensors and devices compared with standard speed control. The algorithm estimates stick-slip of wheels based on estimation of angular acceleration so that the traction force induced by torque of wheel converses between maximum static friction and kinetic friction. Simulations are performed to verify the validity of the algorithm. The proposed traction control algorithm obtained 40.5% reduction of total slip distance and 48.4% reduction of dissipated work on the contact point compared with standard speed control. Furthermore, the algorithm does not require complex wheel-soil interaction model and optimization of robot kinematics.
    No preview · Article · Mar 2015
  • H.D. Choi · C.K. Woo · H.S. Kang · S. Kim · Y.K. Kwak
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    ABSTRACT: The common requirements of rough terrain mobile robots are long-term operation and high mobility in rough terrain to perform difficult tasks. In rough terrain, excessive wheel slip could cause an increase in the amount of dissipated energy at the contact point between the wheel and ground or, even more seriously, the robot could lose all mobility and become trapped. This paper proposes a traction control algorithm that can be independently implemented to each wheel without requiring extra sensors and devices compared with standard velocity control methods. The proposed traction algorithm is analogous to the stick-slip friction mechanism. The algorithm estimates the slippage of wheels by angular acceleration change, and controls the increase or decrease state of torque applied to wheels Simulations are performed to validate the algorithm. The proposed traction control algorithm yielded a 65.4% reduction of total slip distance and 70.6% reduction of power consumption compared with the standard velocity control method.
    No preview · Article · Feb 2009
  • D.Y. Koh · K.H. Hyun · C.K. Woo · H.D. Choi · S.H. Kim
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    ABSTRACT: Various driving mechanisms to adapt to uneven environment have been developed for rescue or reconnaissance. Stair climbing ability is crucial for mobile robots in urban environment missions, since stairs are difficult obstacles. A tracked mechanism has been widely used to maintain the stability of robot's pose and to produce large traction force on uneven terrain. However, it has a drawback of low energy efficiency due to friction force when rotating. Moreover, the size of the stair climbing robot which uses a tracked mechanism is restricted to be reduced to stabilize its motion on the stairway. The mobile robot is affected by this limitation when it operates on uneven terrain. A folding track mechanism is proposed to solve these problems. The mechanism is designed with several articulations surrounded by tracks, used to generate an attack angle when the robot comes near a step. Minimization of contact area between the track and ground is accomplished by folding articulations. Stair climbing process is divided into four phases for separate static analysis. Design parameters are optimized according to geometric limitations for the static analysis. A 3D dynamic analysis was done to verify the static analysis results.
    No preview · Article · Jan 2008
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    ABSTRACT: In this paper, we propose a new wheeled mobile robot (WMR) with a passive linkage-type locomotive mechanism that allows the WMR to adapt passively to rough terrain and climb up stairs, making it ideal for applications such as building inspection, building security, and military reconnaissance. A simple four-bar linkage mechanism and a limited pin joint are proposed after considering two design needs: adaptability and passivity. To improve the WMR’s ability to climb stairs, we divided the stair-climbing motion into several stages, taking into consideration the status of the points of contact between the driving wheels and the step. For each of the suggested stages, a kinetic analysis was accomplished and validated using the multi-body dynamic analysis software package ADAMS. The object functions are presented for the stages that influence the WMR’s ability to climb stairs. The optimization of the object functions is carried out using the multi-objective optimization method.
    No preview · Article · Jul 2007 · Journal of Intelligent and Robotic Systems
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    ABSTRACT: Mobile robots are being developed for building inspection and security, military reconnaissance, and planetary exploration. In such applications, the robot is expected to encounter rough terrain. In rough terrain, it is important for mobile robots to maintain adequate traction as excessive wheel slip causes the robot to lose mobility or even be trapped. This paper proposes a traction control algorithm that can be independently implemented to each wheel without requiring extra sensors and devices compared with standard velocity control methods. The algorithm estimates the stick-slip of the wheels based on estimation of angular acceleration. Thus, the traction force induced by torque of wheel converses between the maximum static friction and kinetic friction. Simulations and experiments are performed to validate the algorithm. The proposed traction control algorithm yielded a 40.5% reduction of total slip distance and 25.6% reduction of power consumption compared with the standard velocity control method. Furthermore, the algorithm does not require a complex wheel-soil interaction model or optimization of robot kinematics.
    No preview · Article · Jan 2007 · Autonomous Robots
  • Source
    K H Kim · H D Choi · S Yoon · K W Lee · H S Ryu · C K Woo · Y K Kwak
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    ABSTRACT: More and more researches on household mobile robots are being undertaken these days. Since commercial cleaning robots are now available for sale to the public, robots are being used in private homes. As the quality of household robots improves, docking stations, which have a variety of uses, including as automatic recharging ports, have become increasingly important. Generally in household robots, cheap infrared sensors are adopted as part of a homing system that is utilized in conjunction with a docking station, enabling the robot to approach and enter the dock successfully. However, systems that use cheap sensors cannot reach their full potential unless they also have a relatively accurate docking system. In this paper, we propose a homing system that utilizes cheap infrared sensors but that can operate in a broad region, and we suggest a passive docking mechanism that can compensate for docking errors. Experimental results using the proposed system show that the robot is able to home in at a radius of up to 2 m around the docking station. Also, the docking mechanism is able to compensate for an offset error of ±5 cm and an angle error of ±30°, and the probability of docking successfully on the first attempt is over 95%.
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