• Journal of Institute of Control, Robotics and Systems
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• v.21 no.8
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• pp.781-787
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• 2015

This paper proposes a hybrid visual servoing algorithm for the object tracking by a mobile robot with the stereo camera. The mobile robot with the stereo camera performs an object recognition and object tracking using the SIFT and CAMSHIFT algorithms for the hybrid visual servoing. The CAMSHIFT algorithm using stereo camera images has been used to obtain the three-dimensional position and orientation of the mobile robot. With the hybrid visual servoing, a stable balance control has been realized by a control system which calculates a desired angle of the center of gravity whose location depends on variations of link rotation angles of the manipulator. A PID controller algorithm has adopted in this research for the control of the manipulator since the algorithm is simple to design and it does not require unnecessary complex dynamics. To demonstrate the control performance of the hybrid visual servoing, real experiments are performed using the mobile manipulator system developed for this research.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.12
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• pp.1182-1188
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• 2010

This paper proposes a precise localization algorithm for a quickly moving mobile robot. In order to localize a mobile robot with active beacon sensors, a relatively long time is needed, since the distance to the beacon is measured using the flight time of the ultrasonic signal. The measurement time does not cause a high error rate when the mobile robot moves slowly. However, with an increase of the mobile robot's speed, the localization error becomes too high to use for accurate mobile robot navigation. Therefore, in this research into high speed mobile robot operations, instead of using two active beacons for localization an active beacon and dual compass are utilized to localize the mobile robot. This new approach resolves the high localization error caused by the speed of the mobile robot. The performance of the precise localization algorithm was verified by comparing it to the conventional method through real-world experiments.

• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.5
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• pp.295-301
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• 2017

Recently, autonomous navigation technology, obstacle recognition, and obstacle collision avoidance technology are actively being developed for an unmanned surface vehicle (USV). The path to move from the current location to the destination should be planned, in order for an USV to autonomously operate safely to its destination. The dynamic window approach (DWA) is a well-known navigation scheme as a local path planning. The DWA algorithm derives the linear velocity and angular velocity by evaluating the destination direction, velocity, and distance from the obstacle. However, because DWA algorithm does not consider tracking the path, when using only the DWA algorithm, the ship may navigate away from the path line after avoiding obstacles. In this paper, we propose an improved DWA algorithm that can follow path line. And we implemented the simulation and compared the existing DWA algorithm with the improved DWA algorithm proposed in this paper. As a result, it is confirmed that the proposed DWA algorithm follows the path line better.

• 전자공학회논문지 IE
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• v.43 no.4
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• pp.52-59
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• 2006

Walking robot is able to move in regular or irregular terrain. It can walk that change adaptive algorithms according to the terrain. Existing papers about adaptive gaits of blind robot are based on intelligent foothold selection. However, this paper proposes a algerian that is based on the variations of stroke and period to adapt the irregular terrain. If thus adaptive algorithms is used, robot can maintain periodic gait walking and constant speed using only force sensor even in the irregular terrain without external sophisticated sensor. In this paper Quadruped robot with 2 DOF in each leg, is walk experiment with the wave gait in regular and irregular terrain. So the adaptive algorithm is proved useful through walk experiment.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.6
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• pp.470-476
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• 2001

This paper presents a new algorithm of path planning and obstacle avoidance for autonomous mobile robots with vision system that is working in unknown environments. Distance variation technique is used in path planning to approach the target and avoid obstacles in work space as well . In this approach, the Sobel operator is employed to detect edges of obstacles and the distances between the mobile robot and the obstacles are measured. Fuzzy rules are used for trajectory planning and obstacle avoidance to improve the autonomy of mobile robots. It is shown by computer simulation that the proposed algorithm is superior to the vector field approach which sometimes traps the mobile robot into some local obstacles. An autonomous mobile robot with single vision is developed for experiments. We also show that the developed mobile robot with the proposed algorithm is navigating very well in complex unknown environments.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.3
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• pp.249-255
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• 2007

Under the situation of a fire, it is difficult for a rescue robot to use sensors such as vision sensor, ultrasonic sensor or laser distance sensor because of diffusion, refraction or block of light and sound by dense smoke. But, braille blocks that are installed for the visaully impaired at public places such as subway stations can be used as a map for autonomous mobile robot's localization and navigation. In this paper, we developed a laser sensor stan device which can detect braille blcoks in spite of dense smoke and integrated the device to the robot developed to carry out rescue mission in various hazardous disaster areas at KIST. We implemented MCL algorithm for robot's attitude estimation according to the scanned data and transformed a braille block map to a topological map and designed a nonlinear path tracking controller for autonomous navigation. From various simulations and experiments, we could verify that the developed laser sensor device and the proposed localization method are effective to autonomous tracking of braille blocks and the autonomous navigation robot system can be used for rescue under fire.

• The Journal of Korea Robotics Society
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• v.9 no.2
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• pp.111-116
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• 2014

Human-robot co-operation becomes increasingly frequent due to the widespread use of service robots. However, during such co-operation, robots have a high chance of colliding with humans, which may result in serious injury. Thus, many solutions were proposed to ensure collision safety, and among them, collision detection algorithms are regarded as one of the most practical solutions. They allow a robot to quickly detect a collision so that the robot can perform a proper reaction to minimize the impact. However, conventional collision detection algorithms required the precise model of a robot, which is difficult to obtain and is subjected to change. Also, expensive sensors, such as torque sensors, are often required. In this study, we propose a novel collision detection algorithm which only requires motor encoders. It detects collisions by monitoring the high-pass filtered version of the velocity error. The proposed algorithm can be easily implemented to any robots, and its performance was verified through various tests.

• The Journal of Korea Robotics Society
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• v.9 no.1
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• pp.11-19
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• 2014

In this paper, an external torque estimation problem in one-degree-of-freedom (1-DOF) flexible-joint robot equipped with a joint-torque sensor is revisited. Since a sensor torque from the joint-torque sensor is distorted by two dynamics having a spring connection, i.e., motor dynamics and link dynamics of a flexible-joint robot, a model-based estimation, rather than a simple linear spring model, should be required to extract external torques accurately. In this paper, an external torque estimation algorithm for a 1-DOF flexible-joint robot is proposed. This algorithm estimates both an actuating motor torque from the motor dynamics and an external link torque from the link dynamics simultaneously by utilizing the flexible-joint robot model and the Kalman filter estimation based on random-walk model. The basic structure of the proposed algorithm is explained, and the performance is investigated through a custom-designed experimental testbed for a vertical situation under gravity.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.11
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• pp.1070-1075
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• 2015

This paper proposes a calibration algorithm for a three-degree-of-freedom (DOF) planar cable-driven parallel robot (CDPR). To evaluate the proposed algorithm, we calibrated winches and an optical tracking sensor, measured the end-effector pose using the optical tracking sensor, and calculated the accurate robot configuration using the measurement information. To conduct an accuracy test on the end-effector pose, we followed guidelines from "Manipulating industrial robots - Performance criteria and related test methods." Through the test, it is verified that the position accuracy can be improved by up to 20% for a $2m{\times}2m$-sized planar cable robot using the proposed calibration algorithm.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.11
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• pp.1665-1674
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• 2013

In this paper, we propose a genetic algorithm(GA) based locomotion method of a quadruped robot with waist joint, which makes a quadruped robot walk on the slop efficiently. In the proposed method, we first derive the kinematic model of a quadruped robot with waist joint and then set the gene and the fitness function for GA. In addition, we determine the best attitude for a quadruped robot and the landing point of a foot in the walk space, which has the optimal energy stability margin(ESM). Finally, we verify the effectiveness of the proposed method by comparing with the performance of the previous method through the computer simulations.