Papers by François Chaumette
2006 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2006
This paper describes an original control law called qualitative servoing. The particularity of th... more This paper describes an original control law called qualitative servoing. The particularity of this method is that no specific desired value is specified for the visual features involved in the control scheme. Indeed, visual features are only constrained to belong to a confident interval, which gives more flexibility to the system. While this formalism can be used for several types of visual features, it is used in this paper for improving the on-line control of the visibility of a target. The principle is to make a compromise between the classical positioning task and the visibility constraint. Experimental results obtained with a six degrees of freedom robot arm are presented, demonstrating the performance of the proposed method.
The Second IEEE and ACM International Symposium on Mixed and Augmented Reality, 2003. Proceedings.
Augmented Reality has now progressed to the point where real-time applications are being consider... more Augmented Reality has now progressed to the point where real-time applications are being considered and needed. At the same time it is important that synthetic elements are rendered and aligned in the scene in an accurate and visually acceptable way. In order to address these issues a real-time, robust and efficient 3D model-based tracking algorithm is proposed for a 'video see through' monocular vision system. The tracking of objects in the scene amounts to calculating the pose between the camera and the objects. Virtual objects can then be projected into the scene using the pose. Here, non-linear pose computation is formulated by means of a virtual visual servoing approach. In this context, the derivation of point-to-curves interaction matrices are given for different features including lines, circles, cylinders and spheres. A local moving edges tracker is used in order to provide real-time tracking of points normal to the object contours. A method is proposed for combining local position uncertainty and global pose uncertainty in an efficient and accurate way by propagating uncertainty. Robustness is obtained by integrating a M-estimator into the visual control law via an iteratively re-weighted least squares implementation. The method presented in this paper has been validated on several complex image sequences including outdoor environments. Results show the method to be robust to occlusion, changes in illumination and misstracking.
The International Journal of Robotics Research, 2002
In this paper we present a method to control the displacement of a robot arm with no propriocepti... more In this paper we present a method to control the displacement of a robot arm with no proprioceptive sensor. The joint positions are not available and this manipulator is usually open-loop controlled. In order to get a more efficient control interface, we propose a closed-loop system based on an eye-to-hand visual servoing approach. We show that, using such an approach, measurement of the manipulator motion with proprioceptive sensors is not required to precisely control the end-effector motion. We propose solutions for position-based control and velocity control of the manipulator. To maintain the end effector in the camera field of view, the camera orientation is also controlled. Various results show the validity and the efficiency of the approach.
IEEE Transactions on Pattern Analysis and Machine Intelligence, 1999
IEEE Transactions on Robotics and Automation, 2002
IEEE Transactions on Automatic Control, 2009
Classical sensor-based control laws are based on the regulation of a set of sensor-based features... more Classical sensor-based control laws are based on the regulation of a set of sensor-based features to a desired reference value. The feature set is generally constant. In this article, we focus on the study of sensor-based control laws whose feature set varies during the servo. In that case, we first show that the classical control laws that use an iterative leastsquare minimization are discontinuous, and cannot be applied to real robots. We then show that these discontinuities are due to the pseudo-inverse operator, which is not continuous at matrix rank change. To solve this problem, we propose a new inversion operator. This operator is equal to the classical pseudo-inverse operator in the continuous cases, and ensures the continuity everywhere. This operator is then used to build a new control law. This general control scheme is applied to visual servoing, to ensure the continuity when some visual features leave the camera field of view. The experiments prove the interest and the validity of our approach.
Classical visual servoing techniques need a strong a priori knowledge of the shape and the dimens... more Classical visual servoing techniques need a strong a priori knowledge of the shape and the dimensions of the observed objects. In this paper, we present how the 2 1/2 D visual servoing scheme we have recently developed, can be used with unknown objects characterized by a set of points. Our scheme is based on the estimation of the camera displacement from two views, given by the current and desired images. Since vision-based robotics tasks generally necessitate to be performed at video rate, we focus only on linear algorithms. Classical linear methods are based on the computation of the essential matrix. In this paper, we propose a different method, based on the estimation of the homography matrix related to a virtual plane attached to the object. We show that our method provides a more stable estimation when the epipolar geometry degenerates. This is particularly important in visual servoing to obtain a stable control law, especially near the convergence of the system. Finally, experimental results confirm the improvement in the stability, robustness, and behaviour of our scheme with respect to classical methods.
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Papers by François Chaumette