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RESIDUAL UNCERTAINTY IN 3-DIMENSIONAL RECONSTRUCTION USING 2-PLANES CALIBRATION AND STEREO METHODS

PATTERN RECOGNITION 1995年第7期28卷 1073-1082页

作者： THAYER, S TRIVEDI, M Electrical and Computer Engineering Department Computer Vision and Robotics Research Laboratory The University of Tennessee Knoxville TN 37996-2100 U.S.A.

A necessary goal in the calibration of any instrument is an indication of how well the particular device performs. In the specific case where a camera system is used in the process of three-dimensional reconstruction or stereopsis, geometric measures of the accuracy, precision, and repeatability of 3-D point measurements give a quantitative evaluation of the success of that algorithm. This paper presents an experimental performance analysis of a traditional calibration algorithm as applied to the problem of three-dimensional vision. The study begins with an analysis of the algorithm in a single camera or monocular system. Monocular analysis concludes with a derivation of error boundaries under different. geometric constraints. Showing how this residual error propagates from the component monocular systems into a three-dimensional reconstruction, a binocular analysis derives the desired performance monitors. The paper concludes with a geometric interpretation of the results.

关键词： STEREOPSIS ACCURACY PRECISION REPEATABILITY MONOCULAR BINOCULAR 2-PLANES CALIBRATION

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CIRCULAR-MELLIN FEATURES FOR TEXTURE SEGMENTATION

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IEEE TRANSACTIONS ON IMAGE PROCESSING 1995年第12期4卷 1629-1640页

作者： RAVICHANDRAN, G TRIVEDI, MM Computer Vision and Robotics Research Laboratory Electrical and Computer Engineering Dept. University of Tennessee Knoxville TN 37996-2100 USA

Texture is an important cue in region-based segmentation of images. In this paper, we provide insight into the development of a new set of distortion-invariant texture operators. These ''circular-Mellin'' operators are invariant to both scale and orientation of the target and represent the spectral decomposition of the image scene in the polar-log coordinate system. Coupled with the unique shift invariance property of the correlator architecture, we show that these circular-Mellin operators can be used for rotation-and scale-invariant feature extraction. We note that while these feature extractors have a functional form that is similar to the Gabor operators, they have distortion-invariant characteristics unlike the Gabor functions that make them more suitable for texture segmentation. A detailed analytical description of these operators and segmentation results to highlight their salient properties are presented.

关键词： Feature extraction Correlation Image segmentation Gabor filters Maximum likelihood detection Correlators Nonlinear filters

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A NEW NEURAL-NETWORK CONTROL TECHNIQUE FOR ROBOT MANIPULATORS

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ROBOTICA 1995年第5期13卷 477-484页

作者： JUNG, S HSIA, TC Robotics Research Laboratory Department of Electrical and Computer Engineering University of California Davis CA 95616 (USA)

A new neural network (NN) control technique for robot manipulators is introduced in this paper. The fundamental robot control technique is the model-based computed-torque control which is subjected to performance degradation due, to model uncertainty. NN controllers have been traditionally used to generate a compensating joint torque to account for the effects of the uncertainties. The proposed NN control approach is conceptually different in that it is aimed at prefiltering the desired joint trajectories before they are used to command the computed-torque-controlled robot system (the plant) to counteract performance degradation due to plant uncertainties. In this framework, the NN controller serves as the inverse model of the plant, which can be trained on-line using joint tracking error. Several variations of this technique introduced. Back-propagation algorithms the NN controller have been developed. Simulation results have demonstrated the excellent tracking performance of the proposed control technique.

关键词： NEURAL NETWORK CONTROL ROBOTS COMPUTED TORQUE

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ROBOT PERFORMANCE-MEASUREMENT AND CALIBRATION USING A 3D computer vision SYSTEM

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ROBOTICA 1995年第4期13卷 327-337页

作者： PREISING, B HSIA, TC Robotics Research Laboratory Department of Electrical and Computer Engineering University of California Davis Davis California 95616 (USA)

Present day robot systems are manufactured to perform within industry accepted tolerances. However, to use such systems for tasks requiring high precision, various methods of robot calibration are generally required. These procedures can improve the accuracy of a robot within a small volume of the robot's workspace. The objective of this paper is to demonstrate the use of a single camera 3D computer vision system as a position sensor in order to perform robot calibration. A vision feedback scheme, termed vision-guided Robot Control (VRC), is described which can improve the accuracy of a robot in an on-line iterative manner. This system demonstrates the advantage that can be achieved by a Cartesian space robot control scheme when end effector position/orientation are actually sensed instead of calculated from the kinematic equations. The degree of accuracy is determined by setting a tolerance level for each of the six robot Cartesian space coordinates. In general, a small tolerance level requires a large number of iterations in order to position the end effector, and a large tolerance level requires fewer iterations. The viability of using a vision system for robot calibration is demonstrated by experimentally showing that the accuracy of a robot can be drastically improved. In addition, the vision system can also be used to determine the repeatability and accuracy of a robot in a simple, efficient, and quick manner. Experimental work with an IBM Electric Drive Robot (EDR) and the proposed vision system produced a 97 and a 145 fold improvement in the position and orientation accuracy of the robot, respectively.

关键词： 3D vision ROBOT PERFORMANCE CALIBRATION POSITION SENSOR

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A 3-DIMENSIONAL LOCALIZER FOR AUTONOMOUS ROBOT VEHICLES

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ROBOTICA 1995年第1期13卷 87-94页

作者： KLEEMAN, L Intelligent Robotics Research Centre Department of Electrical and Computer Systems Engineering Monash University Clayton VIC 3168 Australia

A novel design of a three dimensional localiser intended for autonomous robot vehicles is presented. A prototype is implemented in air using ultrasonic beacons at known positions, and can be adapted to underwater environments where it has important applications, such as deep sea maintenance, data collection and reconnaissance tasks. The paper presents the hardware design, algorithms for position and orientation determination (six degrees of freedom), and performance results of a laboratory prototype. Two appraoches are discussed for position and orientation determination - (i) fast single measurement set techniques and (ii) computationally slower Kalman filter based techniques. The Kalman filter approach allows the incorporation of robot motion information, more accurate beacon modelling and the capability of processing data from more than four beacons, the minimum number required for localisation.

关键词： POSITION ESTIMATION 3-D LOCALIZATION KALMAN FILTERING ULTRASONIC NAVIGATION ORIENTATION UNDERWATER VEHICLES

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EXPERIMENTAL RESULTS ON ADAPTIVE NONLINEAR CONTROL AND INPUT PRESHAPING FOR MULTILINK FLEXIBLE MANIPULATORS

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AUTOMATICA 1995年第1期31卷 83-97页

作者： KHORRAMI, F JAIN, S TZES, A School of Electrical Engineering and Computer Science Control/Robotics Research Laboratory (CRRL) Polytechnic University Brooklyn NY 11201 United States Department of Mechanical Engineering Control/Robotics Research Laboratory (CRRL) Polytechnic University Brooklyn NY 11201 United States

Adaptive input precompensators in conjunction with nonlinear controllers for multi-link flexible manipulators are considered in this paper. In an earlier paper, we had shown that application of a nonlinear inner-loop control reduces the variations in frequencies due to the geometrical configuration for multi-link flexible manipulators. This results in a better performance when input preshaping or any other controller based on a linear model is designed. To improve the performance of the system to parameter variations (e.g. changes in payload), an adaptive version of the advocated controller is utilized. This is achieved by estimating the time of application of the impulses for on-line preshaping and in the case of payload uncertainty, estimation of the payload and real-time adjustment of the nonlinear inner-loop based controller. Frequency domain Time-Varying Transfer Function Estimate (TTFE) and Empirical Transfer Function Estimate (ETFE) system identification algorithms are proposed for estimation of vibrational modes and unknown payload. Experimental results on a two-link flexible manipulator with adaptive nonlinear control and preshaping are provided to show the effectiveness of the advocated controllers. Overall, the present paper completely generalizes the adaptive input preshaping technique for multi-link flexible manipulators.

关键词： FLEXIBLE MANIPULATORS VIBRATION DAMPING NONLINEAR CONTROL INPUT PRESHAPING IDENTIFICATION ADAPTIVE CONTROL

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STEERING 3-INPUT NONHOLONOMIC SYSTEMS - THE FIRE TRUCK EXAMPLE

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INTERNATIONAL JOURNAL OF robotics research 1995年第4期14卷 366-381页

作者： BUSHNELL, LG TILBURY, DM SASTRY, SS Electronics Research Laboratory Department of Electrical Engineering and Computer Sciences University of California at Berkeley Berkeley California 94720

In this article we steer wheeled nonholonomic systems that can be represented in a so-called chained form. Sufficient conditions for converting a multiple-input system with nonholonomic velocity constraints into a multiple-chain, single-generator chained form via state feedback and a coordinate transformation are presented along with sinusoidal and polynomial control algorithms to steer such systems. Our example is the three-input nonholonomic system of a fire truck, or tiller truck. In this three-axle system, the control inputs are the steering velocities of both the first and third (or tiller) axles and the forward driving velocity of the truck. Simulation results are given for parallel parking, left hand turning, right hand turning, and changing lanes. Comparison is made to the same vehicle without tiller steering.

关键词： robotics

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Autonomous mobile robot navigation using fish-eye lenses 3rd

引用

3rd International computer Science Conference, ICSC 1995

作者： Shah, Shishir Aggarwal, J.K. Computer and Vision Research Center Department of Electrical and Computer Engineering The University of Texas at Austin AustinTX78712-1084 United States

ISBN: (纸本)9783540606970

We present an autonomous mobile robot navigation system using stereo fish-eye lenses for navigation in indoor structured environments. The system estimates the three-dimensional (3D) position of significant features in the environment, and by estimating its relative position, navigates through narrow passages and makes turns at the end of corridors. Fish-eye lenses are used to provide a large field of view, which helps in imaging objects close to the robot. The system is implemented and tested in a structured environment at our laboratory. Results from the robot navigation in real environments are presented. © Springer-Verlag Berlin Heidelberg 1995.

关键词： Navigation

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Categorical color projection for robot road following

Categorical color projection for robot road following

引用

IEEE International Conference on robotics and Automation (ICRA)

作者： Nan Zeng J.D. Crisman Robotics & Vision Systems Laboratory Department of Electrical and Computer Engineering Northeastern University Boston MA USA

This paper shows that categorical color developed in Yue Du (1994) is a good representation of color space for some robot vision tasks. The authors use SCARF as a test case to compare 'equivalent' RGB, categorical color, and intensity robot vision algorithms on a difficult robot road following task. SCARF uses a full three-dimensional representation of color space to formulate road and off-road colors. Performing categorical color or intensity projection, the authors can model the road and off-road colors as single dimensional probability density functions. This greatly reduces the time to process the color image. Moreover, the authors show that categorical color is a good representation in that it outperforms an equivalent intensity algorithm on the robot tasks. Categorical color, while it cannot outperform the original RGB algorithm, performs well enough to be used in this particular robot application. Its effectiveness is verified by many experiments on difficult road image sequences.

关键词： Roads Robot vision systems Orbital robotics Color Machine vision Mobile robots Image segmentation Layout Image edge detection Degradation

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A new neural network control technique for robot manipulators

A new neural network control technique for robot manipulator...

引用

American Control Conference (ACC)

作者： Seul Jung T.C. Hsia Robotics Research Laboratory Department of Electrical and Computer Engineering University of California Davis CA USA

A neural network (NN) control technique for robot manipulators is introduced in this paper. The fundamental robot control technique is the model-based computed-torque control which is subjected to performance degradation due to model uncertainty. NN controllers have been traditionally used to generate a compensating joint torque to account for the effects of the uncertainties. The proposed NN control approach is conceptually different in that it is aimed at prefiltering the desired joint trajectories before they are used to command the computed-torque-controlled robot system (the plant) to counteract performance degradation due to plant uncertainties. In this framework, the NN controller serves as the inverse model of the plant, which can be trained online using joint tracking error. Several variations of this basic technique are introduced. Backpropagation training algorithms for the NN controller have been developed. Simulation results have demonstrated the excellent tracking performance of the proposed control technique.

关键词： Neural networks Robot control Manipulators Uncertainty Degradation Torque control Control systems Inverse problems Error correction Backpropagation

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