Browsing by Author "Chang, Yung-Jung"

Now showing 1 - 12 of 12

A Ball-Throwing Robot with Visual Feedback
(2010-01-01)
Hu, Jwu-Sheng
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Chien, Ming-Chih
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Chang, Yung-Jung
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Su, Shyh-Haur
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Kai, Chen-Yu
This work presents a robot system for throwing a ball into a basket. A stereo vision system is used to measure the position of the target in 3D space. The ball-throwing transformation between the input command of the robot system and the target position is built by cubic polynomial. Through ball-throwing transformation with visual feedback for target position, the robot throws the ball toward the target which can randomly move to everywhere in visible field. The percentage of successful ball-throwing for target within three meters was found to be approximately 99%.
A Robotic Ball Catcher with Embedded Visual Servo Processor
(2010-01-01)
Hu, Jwu-Sheng
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Chien, Ming-Chih
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Chang, Yung-Jung
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Chang, Yen-Chung
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Su, Shyh-Haur
In this work we present a robotic ball catcher with embedded visual servo processor. The embedded visual servo processor with powerful parallel computing capability is used as the computation platform to track and triangulate a flying ball's position in 3D based on stereo vision. A recursive least squares algorithm for model-based path prediction of the flying ball is used to determine the catch time and position. Experimental results for real time catching of a flying ball are presented by a 6-DOF robot arm. The percentage of success rate of the robotic ball catcher was found to be approximately 60% for the ball thrown to it from five meters away.
Automatic Calibration of Hand-Eye-Workspace and Camera Using Hand-Mounted Line Laser
(2013-12-01)
Hu, Jwu-Sheng
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Chang, Yung-Jung
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電機工程學系
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電控工程研究所
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Department of Electrical and Computer Engineering
This paper develops a novel calibration method for simultaneously calibrating the intrinsic parameters of a camera and the hand-eye-workspace relationships of an eye-to-hand system using a line laser module. Errors in the parameters of a hand-eye coordination system lead to errors in the position targeting in the control of robots. To solve these problems, the proposed method utilizes a line laser module that is mounted on the hand to project laser beams onto the working plane. As well as calibrating the system parameters, the proposed method is effective when the eye cannot see the hand and eliminates the need for a precise calibration pattern or object. The collected laser stripes in the images must satisfy nonlinear constraints at each hand pose. A closed-form solution is derived by decoupling nonlinear relationships based on the homogeneous transform and parallel plane/line constraints. A nonlinear optimization, which considers all parameters simultaneously without error propagation problem, is to refine the closed-form solution. This two-stage process can be executed automatically without manual intervention. The computer simulation and experiment verify the effectiveness of the proposed method and reveal that using a line laser is more accurate than using a single-point laser.
Calibration and On-line Data Selection of Multiple Optical Flow Sensors for Mobile Robot Localization
(2008)
Hu, Jwu-Sheng
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Chang, Yung-Jung
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Hsu, Yu-Lun
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電控工程研究所
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Institute of Electrical and Control Engineering
This paper proposes a calibration method as well as a computational algorithm to integrate the data of multiple optical flow sensors for 2-dimensional trajectory measurement. Optical flow sensors offer a different kind of odometer as compared with the wheel encoder. Using multiple sensors, it is possible to reduce the effect of measurement uncertainties. Since all sensors are mounted on a rigid body, their measurement data must obey a certain relation. This relation is utilized in this paper and mathematical formulations are developed to realize the computation. It is shown that the calibration procedure can be cast as an optimization problem given measurement data. Further, the rigid-body relation is formulated as a null-space constraint using the calibrated parameters. During operation, unreliable sensor measurements can be removed by accessing the error distance to the null space. Experimental results are presented to support the proposed methods.
Calibration and on-line data selection of multiple optical flow sensors for odometry applications
(2009-01-15)
Hu, Jwu-Sheng
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Chang, Yung-Jung
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Hsu, Yu-Lun
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電控工程研究所
;
Institute of Electrical and Control Engineering
This work proposes a calibration method and a computational algorithm to integrate the data of multiple optical flow sensors for two-dimensional trajectory measurements. Optical flow sensors offer a different kind of odometer as compared to the wheel encoder. Using multiple sensors can reduce the effect of measurement uncertainties. Since all sensors are mounted on a rigid body, their measurement data must obey a certain relation. which is utilized in this work. Additionally, mathematical formulae are developed to realize the computation. Analytical results show that the calibration procedure can be cast as an optimization problem given measurement data. Furthermore, the rigid-body relation is formulated as a null-space constraint using the calibrated parameters. Unreliable sensor measurements can be removed during operation by accessing the error distance to the null space. Experimental results are presented to support the proposed methods. (C) 2008 Elsevier B.V. All rights reserved.
Calibration and on-line data selection of multiple optical flow sensors for odometry applications
(2009-01-15)
Hu, Jwu-Sheng
;
Chang, Yung-Jung
;
Hsu, Yu-Lun
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This work proposes a calibration method and a computational algorithm to integrate the data of multiple optical flow sensors for two-dimensional trajectory measurements. Optical flow sensors offer a different kind of odometer as compared to the wheel encoder. Using multiple sensors can reduce the effect of measurement uncertainties. Since all sensors are mounted on a rigid body, their measurement data must obey a certain relation. which is utilized in this work. Additionally, mathematical formulae are developed to realize the computation. Analytical results show that the calibration procedure can be cast as an optimization problem given measurement data. Furthermore, the rigid-body relation is formulated as a null-space constraint using the calibrated parameters. Unreliable sensor measurements can be removed during operation by accessing the error distance to the null space. Experimental results are presented to support the proposed methods. (C) 2008 Elsevier B.V. All rights reserved.
Calibration of an Eye-to-Hand System Using a Laser Pointer on Hand and Planar Constraints
(2011)
Hu, Jwu-Sheng
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Chang, Yung-Jung
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機械工程學系
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Department of Mechanical Engineering
This work proposes a technique for calibration of an eye-to-hand system. The target of the hand-eye calibration is to estimate the geometric transformation between the hand and the eye. This calibration method further considers camera intrinsic parameters and geometric relations of a working plane in space at the same time. A laser pointer casually mounted on the hand is utilized. By manipulating the robot and projecting the laser beam on a plane of unknown orientations, a batch of related image positions of light-spots are extracted from images of the camera. Since the laser is rigidly mounted and the plane is fixed at each orientation, the geometric parameters and measurement data must obey a certain nonlinear constraints and the solutions of parameters can be estimated accordingly. A close-form solution is developed by decoupling the nonlinear equations into linear forms to compute all of the initial values. As a result, the calibration method does not need any manual initial guess of the unknown parameters. To achieve a higher accuracy, a nonlinear optimization method is implemented to refine the estimation. The advantage of using laser pointer is that this technique can be used for the case when the eye does not see the hand. Experimental results of simulations and real data are presented to show the validity and the simple requirements of the proposed algorithm.
Embedded network-controlled omni-directional motion system with optical flow based navigation
(2007-06-28)
Wu, Li-Wei
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Cheng, Jung-Hung
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Chang, Yung-Jung
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Hu, Jwu-Sheng
The present invention discloses an embedded network-controlled omni-directional motion system with optical flow based navigation, wherein multiple motion units and at least one embedded network control system are installed to the body, and at least one optical flow sensor is installed on the ground-facing surface of the body. The movement of the body is driven by the motion units, and the motion unit has an omni-directional wheel and a motor device. The optical flow sensors detect the state of motion and create optical-flow detection data. The embedded network control system exchanges motion control instructions and optical-flow detection data with an external information-processing unit via a communication network. Further, the motion system of the present invention may also connect with peripheral control devices to increase the control convenience of the system. As the system of the present invention adopts an optical flow based navigation technology, the system of the present invention can be free from the influence of wheel sliding, environmental variation, and accumulated errors and can achieve accurate navigation.
Eye-hand-workspace calibration using laser pointer projection on plane surface
(2012)
Hu, Jwu-Sheng
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Chang, Yung-Jung
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電控工程研究所
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Institute of Electrical and Control Engineering
Purpose - The purpose of this paper is to propose a calibration method that can calibrate the relationships among the robot manipulator, the camera and the workspace. Design/methodology/approach - The method uses a laser pointer rigidly mounted on the manipulator and projects the laser beam on the work plane. Nonlinear constraints governing the relationships of the geometrical parameters and measurement data are derived. The uniqueness of the solution is guaranteed when the camera is calibrated in advance. As a result, a decoupled multi-stage closed-form solution. can be derived based on parallel line constraints, line/plane intersection and projective geometry. The closed-form solution can be further refined by nonlinear optimization which considers all parameters simultaneously in the nonlinear model. Findings - Computer simulations and experimental tests using actual data confirm the effectiveness of the proposed calibration method and illustrate its ability to work even when the eye cannot see the hand. Originality/value - Only a laser pointer is required for this calibration method and this method can work without any manual measurement. In addition, this method can also be applied when the robot is not within the camera field of view.
Kinematic Calibration of Manipulator Using Single Laser Pointer
(2012-01-01)
Hu, Jwu-Sheng
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Wang, Jyun-Ji
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Chang, Yung-Jung
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電子工程學系及電子研究所
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交大工研院聯合研發中心
This paper proposes a robot kinematic calibration system including a laser pointer installed on the manipulator, a stationary camera, and a planar surface. The laser pointer beams to the surface, and the camera observes the projected laser spot. The position of the laser spot is computed according to the geometrical relationships of line-plane intersection. The laser spot position is sensitive to slight difference of the end-effector pose due to the extensibility of laser beam. Inaccurate kinematic parameters cause inaccurate calculation of the end-effector pose, and then the laser spot position by the forward estimation is deviated from the one by camera observation. For calibrating the robot kinematics, the optimal solution of kinematic parameters is obtained by minimizing the laser spot position difference between the forward estimation and camera measurement via the nonlinear optimization method. The proposed kinematic calibration system is cost-efficient and flexible for any manipulator. The proposed method is validated by simulation and experiment.
Spatial trajectory tracking control of omni-directional wheeled robot using optical flow sensors
(2007)
Hu, Jwu-Sheng
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Cheng, Jung-Hung
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Chang, Yung-Jung
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電控工程研究所
;
Institute of Electrical and Control Engineering
This study presents a method of controlling a mobile robot of omni-directional wheels. Two optical flow sensors are installed on the chassis of the robot to obtain motion information relative to the world coordinate. Due to wheel slip, the kinematic relation from the wheel speed to the robot speed no longer holds. An extremum seeking algorithm is proposed to cope with the unknown friction when the robot tries to follow a prescribed trajectory. Further, a spatial tracking algorithm is proposed to modify the velocity commands to achieve a better performance in trajectory following. Lastly, a simple obstacle avoidance algorithm is also proposed based on the optical flow sensor measurement. Experiments are conducted for various driving conditions including different road surfaces to show the effectiveness of the proposed methods.
Spatial trajectory tracking control of omni-directional wheeled robot using optical flow sensors
(2007)
Hu, Jwu-Sheng
;
Cheng, Jung-Hung
;
Chang, Yung-Jung
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This study presents a method of controlling a mobile robot of omni-directional wheels. Two optical flow sensors are installed on the chassis of the robot to obtain motion information relative to the world coordinate. Due to wheel slip, the kinematic relation from the wheel speed to the robot speed no longer holds. An extremum seeking algorithm is proposed to cope with the unknown friction when the robot tries to follow a prescribed trajectory. Further, a spatial tracking algorithm is proposed to modify the velocity commands to achieve a better performance in trajectory following. Lastly, a simple obstacle avoidance algorithm is also proposed based on the optical flow sensor measurement. Experiments are conducted for various driving conditions including different road surfaces to show the effectiveness of the proposed methods.