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ABSTRACT: The aim of this paper is to study force and position control of kinematic parallel machines. Relying on a recent work showing
that computed torque control in Cartesian space is suitable for parallel structures, we propose a parallel force position
control scheme of a parallel robot based on the visual servoing of the end effector pose. Simulation results show the efficiency
of the proposed approach.
KeywordsParallel robots–Force control–Parallel control–Visual servoing
Meccanica 04/2012; 46(1):195-205. · 1.56 Impact Factor
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ABSTRACT: In this paper, we propose a visual path following control scheme for wheeled mobile robots based on the epipolar geometry. The control law only requires the position of the epipole computed between the current and target views along the sequence of a visual memory. The proposed approach has two main advantages: explicit pose parameters decomposition is not required and the rotational velocity is smooth or eventually piece-wise constant avoiding discontinuities that generally appear when the target image changes. The translational velocity is adapted as required for the path and the approach is independent of this velocity. Furthermore, our approach is valid for all cameras obeying the unified model, including conventional, central catadioptric and some fisheye cameras. Simulations as well as real-world experiments with a robot illustrate the validity of our approach.
Intelligent Robots and Systems (IROS), 2010 IEEE/RSJ International Conference on; 11/2010
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ABSTRACT: This paper proposes a generic decoupled image-based control scheme for cameras obeying the unified projection model. The scheme is based on the spherical projection model. Invariants to rotational motion are computed from this projection and used to control the translational degrees of freedom (DOFs). Importantly, we form invariants that decrease the sensitivity of the interaction matrix to object-depth variation. Finally, the proposed results are validated with experiments using a classical perspective camera as well as a fisheye camera mounted on a 6-DOF robotic platform.
IEEE Transactions on Robotics 09/2010; · 2.54 Impact Factor
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ABSTRACT: Vision has often been considered as not suitable for dynamic control of robots. The experimental results presented in this paper show that it is possible to perform better with a vision based dynamic control than with a model-based control. These results were obtained using a Cartesian computed torque control fed back, without any joint sensing, by a novel Cartesian pose and velocity estimator. The latter is designed as a virtual visual servoing scheme based on sequential acquisition of sub-images and a constant acceleration motion assumption.
Robotics and Automation (ICRA), 2010 IEEE International Conference on; 06/2010
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ABSTRACT: This paper concerns the stability analysis of image-based visual servoing control laws with respect to uncertainties on the 3-D parameters needed to compute the interaction matrix for any calibrated central catadioptric camera. In the recent past, research on image-based visual servoing has been concentrated on potential problems of stability and on robustness with respect to camera-calibration errors. Only little attention, if any, has been devoted to the robustness of image-based visual servoing to estimation errors on the 3-D structure. It is generally believed that a rough approximation of the 3-D structure is sufficient to ensure the stability of the control law. In this paper, we prove that this is not always true and that an extreme care must be taken when approximating the depth distribution to ensure stability of the image-based control law. The theoretical results are obtained not only for conventional pinhole cameras but for the entire class of central catadioptric systems as well.
IEEE Transactions on Robotics 03/2010; · 2.54 Impact Factor
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ABSTRACT: This paper presents a vision-based navigation strategy for a vertical take-off and landing (VTOL) unmanned aerial vehicle (UAV) using a single embedded camera observing natural landmarks. In the proposed approach, images of the environment are first sampled and stored as a set of ordered key images (visual path) and organized providing a visual memory of the environment. The robot navigation task is then defined as a concatenation of visual path subsets (called visual route) linking the current observed image and a target image belonging to the visual memory. The UAV is controlled to reach each image of the visual route using a vision-based control law adapted to its dynamic model and without explicitly planning any trajectory. This framework is largely substantiated by experiments with a X4-flyer equipped with a fisheye camera.
Intelligent Robots and Systems, 2009. IROS 2009. IEEE/RSJ International Conference on; 11/2009
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ABSTRACT: This paper presents a high speed visual tracking method based on non simultaneous subimages acquisition. This method is formulated as a virtual visual servoing scheme. The sequential acquisition of regions of interest has a double benefit on visual servoing. The first one is that this acquisition method allows to increase the visual control sampling frequency by reducing the data amount to acquire and to transmit by the camera. The second one is that the associated image projection model depends on the observed object pose and velocity. Thanks to this property, a new vision-based control law can be defined. The particularity of this control law is that the control output consists of the kinematic and the dynamic twists. This allows to enhance the control performance in trajectory tracking applications. The experimental results in high speed visual tracking application show the effectiveness of this approach.
Intelligent Robots and Systems, 2009. IROS 2009. IEEE/RSJ International Conference on; 11/2009
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ABSTRACT: In this paper, we present a complete framework for autonomous vehicle navigation using a single camera and natural landmarks. When navigating in an unknown environment for the first time, usual behavior consists of memorizing some key views along the performed path to use these references as checkpoints for future navigation missions. The navigation framework for the wheeled vehicles presented in this paper is based on this assumption. During a human-guided learning step, the vehicle performs paths that are sampled and stored as a set of ordered key images, as acquired by an embedded camera. The visual paths are topologically organized, providing a visual memory of the environment. Given an image of the visual memory as a target, the vehicle navigation mission is defined as a concatenation of visual path subsets called visual routes. When autonomously running, the control guides the vehicle along the reference visual route without explicitly planning any trajectory. The control consists of a vision-based control law that is adapted to the nonholonomic constraint. Our navigation framework has been designed for a generic class of cameras (including conventional, catadioptric, and fisheye cameras). Experiments with an urban electric vehicle navigating in an outdoor environment have been carried out with a fisheye camera along a 750-m-long trajectory. Results validate our approach.
IEEE Transactions on Intelligent Transportation Systems 10/2009; · 3.45 Impact Factor
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ABSTRACT: This paper extends the recent work proposed in [21]. In this work, it has been noted that three visual features (to control three degrees of freedom) obtained from the spherical projection of 3D spheres allows nice decoupling properties and global stability. However, even if such an approach is theoretically attractive, it is limited by a major practical issue since spherical objects have to be observed while only three degrees of freedom can be controlled. In this paper, we show that similar properties can be obtained by observing a set of points. The basic idea is to build a virtual 3D sphere from two 3D points and to analyse its related spherical projection. Furthermore, to control the six degrees of freedom a 2D 1/2 control scheme is proposed which allows us to fully decouple rotational motions from translational motions.
Robotics and Automation, 2009. ICRA '09. IEEE International Conference on; 06/2009
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ABSTRACT: In this paper a generic decoupled imaged-based control scheme for calibrated cameras obeying the unified projection model is proposed. The proposed decoupled scheme is based on the surface of object projections onto the unit sphere. Such features are invariant to rotational motions. This allows the control of translational motion independently from the rotational motion. Finally, the proposed results are validated with experiments using a classical perspective camera as well as a fisheye camera mounted on a 6 dofs robot platform.
Robotics and Automation, 2009. ICRA '09. IEEE International Conference on; 06/2009
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ABSTRACT: This paper deals with the visual control of the Gough-Stewart platform using a central catadioptric camera observing the platform's legs. This allows a large field of view to be obtained and avoids the occlusion problems observed when a classical perspective camera is used. An automatic and simple method to detect the projections of the leg in the image is also proposed. The control scheme presented here is shown to encompass the classical perspective camera case, as well as catadioptric ones. Finally, experimental results comparing two kinds of visual features (leg directions and leg edges) are described.
IEEE Transactions on Robotics 03/2009; · 2.54 Impact Factor
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ABSTRACT: In this paper, we present a complete framework for autonomous indoor robot navigation. We show that autonomous navigation is possible in indoor situation using a single camera and natural landmarks. When navigating in an unknown environment for the first time, a natural behavior consists on memorizing some key views along the performed path, in order to use these references as checkpoints for a future navigation mission. The navigation framework for wheeled robots presented in this paper is based on this assumption. During a human-guided learning step, the robot performs paths which are sampled and stored as a set of ordered key images, acquired by an embedded camera. The set of these obtained visual paths is topologically organized and provides a visual memory of the environment. Given an image of one of the visual paths as a target, the robot navigation mission is defined as a concatenation of visual path subsets, called visual route. When running autonomously, the control guides the robot along the reference visual route without explicitly planning any trajectory. The control consists on a vision-based control law adapted to the nonholonomic constraint. The proposed framework has been designed for a generic class of cameras (including conventional, catadioptric and fish-eye cameras). Experiments with a AT3 Pioneer robot navigating in an indoor environment have been carried on with a fisheye camera. Results validate our approach.
Control, Automation, Robotics and Vision, 2008. ICARCV 2008. 10th International Conference on; 01/2009
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ABSTRACT: In this paper, we present a method to efficiently manage visual memory for autonomous vehicle navigation in large scale environments. It relies on two crucial issues for real-time navigation: an efficient organisation of the memory and small computational cost. A software platform (SoViN) dedicated to visual memory management and navigation strategies (including vision-based memory building, localization and navigation) has been developed to fulfill these requirements. We show that using this software architecture makes possible real-time navigation in large-scale outdoor situation using a single camera and natural landmarks.
Intelligent Robots and Systems, 2008. IROS 2008. IEEE/RSJ International Conference on; 10/2008
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ABSTRACT: In this paper, we consider the problem of controlling a 6 DOF holonomic robot and a nonholonomic mobile robot from the projection of 3-D straight lines in the image plane of central catadioptric systems. A generic central catadioptric interaction matrix for the projection of 3-D straight lines is derived using an unifying imaging model valid for an entire class of cameras. This result is exploited to design an image-based control law that allows us to control the 6 DOF of a robotic arm. Then, the projected lines are exploited to control a nonholonomic robot. We show that as when considering a robotic arm, the control objectives are mainly based on catadioptric image feature and that local asymptotic convergence is guaranteed. Simulation results and real experiments with a 6 DOF eye-to-hand system and a mobile robot illustrate the control strategy.
IEEE Transactions on Robotics 07/2008; · 2.54 Impact Factor
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ABSTRACT: This paper deals with the efficient second order minimization (ESM) and the image-based visual servoing schemes. In other word, it deals with the minimization based on the pseudo-inverses of the mean of the Jacobians or on the mean of Jacobian Pseudo-inverses. Chronologically, it has been noted by Tahri and Chaumette (2003) that the (ESM) improves generally the system behavior compared to the case where only the simple Jacobian Pseudo- inverses is used. Subsequently, a mathematical explanation has been given by Malis (2004). In this paper, the proofs given by Malis are considered to deal with their validity. It will be shown that there is a limitation to the the validity of this method and some precautions should be taken, for adequate application of it. In other words, we will show that the use of ESM does not necessary ensures a better system behavior, especially in the cases where large rotational motions are considered.
Robotics and Automation, 2008. ICRA 2008. IEEE International Conference on; 06/2008
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ABSTRACT: In this paper a new decoupled imaged-based control scheme is proposed from projection onto a unit sphere. This control scheme is based on moment invariants to 3D rotational motion. This allows the control of translational motion independently of the rotational one. First, the analytical form of the interaction matrix related to the spherical moments is derived. It is based on the projection of a set of points onto a unit sphere. From the spherical moment, six features are presented to control the full 6 degrees of freedom. Finally, the results are validated through realistic simulation results.
Robotics and Automation, 2008. ICRA 2008. IEEE International Conference on; 06/2008
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ABSTRACT: An efficient method for global robot localization in a memory of omnidirectional images is presented. This method is valid for indoor and outdoor environments and not restricted to mobile robots. The proposed strategy is purely vision-based and uses as reference a set of prerecorded images (visual memory). The localization consists on finding in the visual memory the image which best fits the current image. We propose a hierarchical process combining global descriptors computed onto cubic interpolation of triangular mesh and patches correlation around Harris corners. To evaluate this method, three large images data sets have been used. Results of the proposed method are compared with those obtained from state-of-the-art techniques by means of 1) accuracy, 2) amount of memorized data required per image and 3) computational cost. The proposed method shows the best compromise in term of those criteria.
Robotics and Automation, 2008. ICRA 2008. IEEE International Conference on; 06/2008
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ABSTRACT: This paper presents a novel method for high speed pose and velocity computation from visual sensor. The main problem in high speed vision is the bottleneck phenomenon which limits the video rate transmission. The proposed approach circles the problem out by increasing the information density instead of the data rate transmission. This strategy is based on a rotary sequential acquisition of selected regions of interest (ROI) which provides space-time data. This acquisition mode induces an image projection deformation of dynamic objects. This paper shows how to use this artifact for the simultaneous measure of both pose and velocity, at the same frequency as the ROI's acquisition one.
Robotics and Automation, 2008. ICRA 2008. IEEE International Conference on; 06/2008
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ABSTRACT: Omnidirectional cameras have a wide field of view and are thus used in many robotic vision tasks. An omnidirectional view may be acquired by a fisheye camera which provides a full image compared to catadioptric visual sensors and do not increase the size and the weakness of the imaging system with respect to perspective cameras. We prove that the unified model for catadioptric systems can model fisheye cameras with distortions directly included in its parameters. This unified projection model consists on a projection onto a virtual unitary sphere, followed by a perspective projection onto an image plane. The validity of this assumption is discussed and compared with other existing models. Calibration and partial Euclidean reconstruction results help to confirm the validity of our approach. Finally, an application to the visual servoing of a mobile robot is presented and experimented.
Intelligent Robots and Systems, 2007. IROS 2007. IEEE/RSJ International Conference on; 12/2007
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ABSTRACT: This paper presents a hybrid decoupled vision-based control scheme valid for the entire class of central catadioptric sensors (including conventional perspective cameras). First, we consider the structure from motion problem using imaged 3D points. Geometrical relationships are exploited to enable a partial Euclidean reconstruction by decoupling the interaction between translation and rotation components of a homography matrix. The information extracted from the homography are then used to design a control law which allow us to fully decouple rotational motions from translational motions. Real time experimental results using an eye-to-hand robotic system with a paracatadioptric camera are presented and confirm the validity of our approach.
Robotics and Automation, 2007 IEEE International Conference on; 05/2007
