• Journal of the Korean Society of Industry Convergence
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• v.17 no.3
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• pp.151-169
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• 2014

We propose a new technique for autonomous navigation and travelling of mobile robot based on ultrasonic sensors through the narrow labyrinth that leave only distance of a few centimeters on each side between the guides and the robot. In our current implementation the ultrasonic sensor system fires at a rate of 100 ms, that is, each of the 8 sensors fires once during each 100 ms interval. This is a very good firing rate, implemented here for optimal performance. This paper presents an extensively tested and verified solution to the problem of obstacle avoidance. Our solution is based on the optimal placement of ultrasonic sensors at strategic locations around the robot. Both the sensor location and the associated navigation algorithm are defined in such a way that only the accurate radial sonar data is used for accurate travelling.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.8
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• pp.696-703
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• 2005

Since most autonomous mobile robots are powered by a battery, it is important to increase the continuous operating time without recharging. This can be achieved by improving the energy efficiency of a mobile robot, but little research on energy efficiency has been performed. This paper proposes two methods for improving the energy efficiency of an omnidirectional mobile robot.. One method is to realize a continuously variable transmission (CVT) by adopting the mechanism of steerable omnidirectional wheels. The other is the proposed steering algorithm in which wheel arrangement of the mobile robot is continuously adjusted so as to obtain the maximum energy efficiency of the motors during navigation. In addition, new omnidirectional wheels which can be transformed to the conventional wheels depending on the driving conditions are proposed to compensate for less efficient omnidirectional drive mode. Various tests show that motion control of the OMR-SOW works satisfactorily and the proposed steering algorithm for CVT can provide higher energy efficiency than the algorithm using a fixed steering angle. In addition, it is shown that the differential drive mode can give better energy efficiency than the omnidirectional drive mode.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.799-807
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• 2014

This paper describes the development of an indoor locomotion assistive robot, Ball-Chair, comprising a novel drive system. This robot facilitates locomotion assistive operation in narrow spaces, in which common wheelchairs cannot move easily. The Ball-Chair has two main features: its structural feature and driving mechanism. The exoskeleton frames of the Ball-Chair have been designed with octagonal shapes resembling a circle, for minimizing its volume and weight. Additionally, all its driving parts (including the ball) are mounted within of the robot to enhance its safety. The Ball-Chair features a reverse ball-mouse driving mechanism comprising two driving omni-wheels in the x- and y-axes. By controlling the speed of each omni-wheel, a holonomic driving system that can facilitate omnidirectional locomotion has been achieved using only two wheels. The effective movement of the Ball-Chair in any direction within narrow indoor spaces was experimentally verified. The paper outlines the development procedure in detail.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.5
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• pp.487-495
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• 2012

In this paper, a Smart Home Service Robot, McBot II, which performs mess-cleanup function etc. in house, is designed much more optimally than other service robots. It is newly developed in much more practical system than McBot I which we had developed two years ago. One characteristic attribute of mobile platforms equipped with a set of dependent wheels is their omni- directionality and the ability to realize complex translational and rotational trajectories for agile navigation in door. An accurate coordination of steering angle and spinning rate of each wheel is necessary for a consistent motion. This paper develops trajectory controller of 3-wheels omni-directional mobile robot using fuzzy azimuth estimator. A specialized anthropomorphic robot manipulator which can be attached to the housemaid robot McBot II, is developed in this paper. This built-in type manipulator consists of both arms with 4 DOF (Degree of Freedom) each and both hands with 3 DOF each. The robotic arm is optimally designed to satisfy both the minimum mechanical size and the maximum workspace. Minimum mass and length are required for the built-in cooperated-arms system. But that makes the workspace so small. This paper proposes optimal design method to overcome the problem by using neck joint to move the arms horizontally forward/backward and waist joint to move them vertically up/down. The robotic hand, which has two fingers and a thumb, is also optimally designed in task-based concept. Finally, the good performance of the developed McBot II is confirmed through live tests of the mess-cleanup task.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1525-1530
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• 2014

In this research, we describe teaching based sweeping control for grinder robot has been proposed as a system which is suitable to work utilizing pressure sensitive alternative to human. Teaching method is used for grinder robots operations because of their position accuracy, path accuracy, and machining reaction force. A grinder robot for two-dimensional iron plate was developed on the basis of an force sensor based teaching method. An automatic-path-generation method and experimental results using specific points was adopted to reduce the number of teaching points and time. And also, in order to determine the proper machining conditions, various machining conditions such as grinder-wheel rotation speed and robot moving speed, were evaluated.

• Journal of Advanced Navigation Technology
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• v.18 no.2
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• pp.134-141
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• 2014

Mobile robots use various sensors for navigation such as wheel encoder, vision sensor, sonar, and laser sensors. Dead reckoning is used with wheel encoder, resulting in the accumulation of positioning errors. For that reason wheel encoder can not be used alone. Too much information of vision sensors leads to an increase in the number of features and complexity of perception scheme. Also Sonar sensor is not suitable for positioning because of its poor accuracy. On the other hand, laser sensor provides accurate distance information relatively. In this paper we propose to extract the angular information from the distance information of laser range finder and use the Kalman filter that match the heading and distance of the laser range finder and those of wheel encoder. For laser scanner with one feature point error may increase much when the feature point is variant or jumping to a new feature point. To solve the problem, we propose to use two feature points and show that the positioning error can be reduced much.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.629-635
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• 2012

Tracked robots usually have poor localization performance because of slippage of their tracks. This study proposes a new localization method for tracked robots that uses fuzzy fusion of stereo-camera-based visual odometry and encoder-based wheel odometry. Visual odometry can be inaccurate when an insufficient number of visual features are available, while the encoder is prone to accumulating errors when large slips occur. To combine these two methods, the weight of each method was controlled by a fuzzy decision depending on the surrounding environment. The experimental results show that the proposed scheme improved the localization performance of a tracked robot.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.3
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• pp.9-18
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• 2000

This paper presents methods for reducing odometer errors caused by kinematic imperfections in wheeled mobile robots. Wheel diameters and wheelbase are corrected by using encoders without landmarks. And a new velocity trajectory is proposed that compensates for an orientation error due to acceleration-resolution constraints on motor controllers. Based on this velocity trajectory, the wheel velocity of one out of two driven wheels may be changed by the traveled distance of the mobile robot. It is shown that a wheeled mobile robot can't move along a straight line exactly, even if kinematic correction are achieved perfectly, and this phenomenon is attributable to acceleration-resolution constraints on motor controllers. We experiment on a wheeled mobile robot with 2 d.o.f. and discuss the results.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.4
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• pp.319-326
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• 2014

Accurate estimation of the robot's position has an important role in autonomous navigation. Odometry is one of the most widely used techniques for mobile robot positioning. However, odometry has a well-known drawback that the position errors are accumulated when the travel distance increases. The UMBmark method is the conventional odometry calibration scheme for two wheel differential mobile robots. In the UMBmark method, the approximations for small angles are used in order to simplify the calculations. In this paper, we propose the new calibration scheme by using experimental orientation errors. Kinematic parameters can be calculated accurately without approximations by using experimental orientation errors. The numerical simulation and experimental results show that the odometry accuracy can be improved by the proposed method.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.323-324
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• 2008

In this paper, we present performance comparison of two methods to localize multiple robots. One is extended Kalman filter and the other is constraint propagation technique. Extended Kalman filter is conventional probabilistic method which gives the sub-optimal estimation rather than guarantee any boundary for true position of robot. In case of constraint propagation, it can give a boundary containing true robot position value. Especially, we deal with cooperative localization problem in outdoor environment for multiple robots equipped with GPS, gyro meter, wheel encoder. In simulation results, we present strength and weakness for localization methods based on extend Kalman filter and constraint propagation technique.