The Experts below are selected from a list of 4221 Experts worldwide ranked by ideXlab platform
Gaurav S Sukhatme - One of the best experts on this subject based on the ideXlab platform.
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simultaneous mapping and stereo Extrinsic Parameter calibration using gps measurements
International Conference on Robotics and Automation, 2011Co-Authors: Jonathan Kelly, Larry Matthies, Gaurav S SukhatmeAbstract:Stereo vision is useful for a variety of robotics tasks, such as navigation and obstacle avoidance. However, recovery of valid range data from stereo depends on accurate calibration of the Extrinsic Parameters of the stereo rig, i.e., the 6-DOF transform between the left and right cameras. Stereo self-calibration is possible, but, without additional information, the absolute scale of the stereo baseline cannot be determined. In this paper, we formulate stereo Extrinsic Parameter calibration as a batch maximum likelihood estimation problem, and use GPS measurements to establish the scale of both the scene and the stereo baseline. Our approach is similar to photogrammetric bundle adjustment, and closely related to many structure from motion algorithms. We present results from simulation experiments using a range of GPS accuracy levels; these accuracies are achievable by varying grades of commercially-available receivers. We then validate the algorithm using stereo and GPS data acquired from a moving vehicle. Our results indicate that the approach is promising.
Hanqi Zhuang - One of the best experts on this subject based on the ideXlab platform.
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a self calibration approach to Extrinsic Parameter estimation of stereo cameras
Robotics and Autonomous Systems, 1995Co-Authors: Hanqi ZhuangAbstract:Abstract A self-calibration technique is proposed in this paper to estimate Extrinsic Parameters of a stero camera system. This technique does not require external 3D measurements of precision calibration points. Furthermore, it is conceptually simple and easy to implement. It has applications in such areas as autonomous vehicle navigation, robotics and computer vision. The proposed approach relies solely on distance measurements of a fixed-length object, say a stick. While the object is moved in the 3D space, the image coordinates of the end points of the object are extracted from the image sequence. A cost function that relates the unknown Parameters to the measurement residuals is formulated. A nonlinear least squares algorithm is then applied to compute the Parameters by minimizing the cost function, using the measured image coordinates and the known length of the object. Simulation studies in this papers answer questions such as the number of iterations needed for the algorithm to converge, the number of measurements needed for a robust estimation, and noise sensitivities of the algorithm.
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a self calibration approach to Extrinsic Parameter estimation of stereo cameras
International Conference on Robotics and Automation, 1994Co-Authors: Hanqi ZhuangAbstract:A self-calibration technique is proposed in this paper to estimate Extrinsic Parameters of a stereo camera system. This technique does not require external 3D measurements of precision calibration points. Furthermore, it is conceptually simple and easy to implement. It has applications in such areas as autonomous vehicle navigation, robotics and computer vision. The proposed approach relies solely on distance measurements of a fixed-length object, say a stick. While the object is moved in the 3D space, the image coordinates of the object end points are extracted from the image sequence. A cost function that relates unknown Parameters to measurement residuals is formulated. A nonlinear least squares algorithm is then applied to compute the Parameters by minimizing the cost function, using the measured image coordinates and the known length of the object. Simulation studies in this papers answer questions such as the number of iterations needed for the algorithm to converge, the number of measurements needed for a robust estimation, singularity cases, and noise sensitivities of the algorithm. >
Hailin Huang - One of the best experts on this subject based on the ideXlab platform.
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online Extrinsic Parameter calibration for robotic camera encoder system
IEEE Transactions on Industrial Informatics, 2019Co-Authors: Xuefeng Wang, Haoyao Chen, Hailin HuangAbstract:Cameras and encoders are widely used in mobile robots, and Extrinsic Parameter calibration of these sensors is crucial in practical performance. The existing approaches mainly rely on manual measurements, accurate computer-aided design (CAD) models, or carefully designed artificial landmarks. This paper presents a novel approach for automatically calibrating the Extrinsic Parameters of the robotic camera–encoder system. The approach first calculates a coarse estimation of the external Parameters as well as the scale of the visual system, via free-scale hand–eye calibration of the camera and odometer. However, the coarse calibration result and scale of the visual system do not satisfy the accuracy requirement for further mobile robots’ applications such as localization and navigation. A nonlinear optimization algorithm that considers both bundle adjustment and odometer measurement error functions is developed to refine the Extrinsic Parameter calibration result. This coarse-fine approach is computationally efficient and can achieve online calibration during the vehicle motion automatically. Furthermore, it can realize the calibration without using any artificial landmark or prior knowledge about CAD models. Finally, comparisons to other classic calibration approaches are performed with a series of simulations and experiments to illustrate the effectiveness of the approach.
Jonathan Kelly - One of the best experts on this subject based on the ideXlab platform.
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simultaneous mapping and stereo Extrinsic Parameter calibration using gps measurements
International Conference on Robotics and Automation, 2011Co-Authors: Jonathan Kelly, Larry Matthies, Gaurav S SukhatmeAbstract:Stereo vision is useful for a variety of robotics tasks, such as navigation and obstacle avoidance. However, recovery of valid range data from stereo depends on accurate calibration of the Extrinsic Parameters of the stereo rig, i.e., the 6-DOF transform between the left and right cameras. Stereo self-calibration is possible, but, without additional information, the absolute scale of the stereo baseline cannot be determined. In this paper, we formulate stereo Extrinsic Parameter calibration as a batch maximum likelihood estimation problem, and use GPS measurements to establish the scale of both the scene and the stereo baseline. Our approach is similar to photogrammetric bundle adjustment, and closely related to many structure from motion algorithms. We present results from simulation experiments using a range of GPS accuracy levels; these accuracies are achievable by varying grades of commercially-available receivers. We then validate the algorithm using stereo and GPS data acquired from a moving vehicle. Our results indicate that the approach is promising.
J D Menldl - One of the best experts on this subject based on the ideXlab platform.
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impact of Extrinsic and intrinsic Parameter fluctuations on cmos circuit performance
IEEE Journal of Solid-state Circuits, 2000Co-Authors: Keith Bowman, Xinghai Tang, John C Eble, J D MenldlAbstract:The yield of CMOS logic circuits satisfying a specific high performance requirement is demonstrated to be significantly influenced by the magnitude of critical-path delay deviations due to both Extrinsic and intrinsic Parameter fluctuations. To evaluate the impact of these Parameter fluctuations, a static CMOS critical-path delay distribution is calculated from rigorously derived device and circuit models that enable projections for future technology generations. Two possible options are explored to attain a desired yield: (1) reduce performance by operating at a lower clock frequency; and (2) increase the supply voltage and, consequently, power dissipation, to satisfy the nominal critical-path delay. For the 50-nm technology generation, the delay and power dissipation increases are 12%-29% and 22%-6%, respectively, for Extrinsic Parameter standard deviations ranging from (a) 5% for effective channel length and 0% for gate oxide thickness and channel doping concentration to (b) 10% for effective channel length and 5% for gate oxide thickness and channel doping concentration. Combining both Extrinsic and intrinsic fluctuations, the delay and power dissipation increase to 18%-32% and 31%-53%, respectively, thus demonstrating the significance of including the random dopant placement effect in future CMOS logic designs.
