Vector-based dynamic modeling and control of the quattro parallel robot by means of leg orientations.

International audienceOne of the key steps in high-speed control of a parallel robot is to define an efficient dynamic model. It is usually not easy to have such a model for parallel robots, since many of them have complex structures. Here, we propose a vector-based approach, which employs the robot leg orientations, to obtain a simplified inverse dynamic model. At the least, this vector-based methodology is pioneering, when combined with the observation of orientations by a calibrated camera, in the sense of solving the entire control-oriented (hard) modeling problem, both kinematics and dynamics, in an almost algebraic manner through the knowledge of only a nominal set of image features: the edges of the robot legs and their time derivatives. Proposed method is verified on a simulator of the Quattro robot with a computed torque control where the leg orientations are steered

Quoi de neuf en asservissement visuel depuis les JNRR'03 ?

National audienceCet article de synthèse présente les avancées réalisées en France au cours de ces quatre dernières années dans le domaine de l'asservissement visuel

Dynamic visual servoing from sequential regions of interest acquisition.: On behalf of: Multimedia Archives Dynamic visual servoing from sequential regions of interest acquisition.

International audienceOne of the main drawbacks of vision-based control that remains unsolved is the poor dynamic performances caused by the low acquisition frequency of the vision systems and the time latency due to processing. We propose in this paper to face the challenge of designing a high-performance dynamic visual servo control scheme. Two versatile control laws are developed in this paper: a position-based dynamic visual servoing and an image-based dynamic visual servoing. Both control laws are designed to compute the control torques exclusively from a sequential acquisition of regions of interest containing the visual features to achieve an accurate trajectory tracking. The presented experiments on vision-based dynamic control of a high-speed parallel robot show that the proposed control schemes can perform better than joint-based computed torque control

Vision-based trajectory control of unsensored robots to increase functionality, without robot hardware modication

In nuclear decommissioning operations, very rugged remote manipulators are used, which lack proprioceptive joint angle sensors. Hence these machines are simply tele-operated, where a human operator controls each joint of the robot individually using a teach pendant or a set of switches. Moreover, decommissioning tasks often involve forceful interactions between the environment and powerful tools at the robot's end-effector. Such interactions can result in complex dynamics, large torques at the robot's joints, and can also lead to erratic movements of a mobile manipulator's base frame with respect to the task space. This Thesis seeks to address these problems by, firstly, showing how the configuration of such robots can be tracked in real-time by a vision system and fed back into a trajectory control scheme. Secondly, the Thesis investigates the dynamics of robot-environment contacts, and proposes several control schemes for detecting, coping with, and also exploiting such contacts. Several contributions are advanced in this Thesis. Specifically a control framework is presented which exploits the constraints arising at contact points to effectively reduce commanded torques to perform tasks; methods are advanced to estimate the constraints arising from contacts in a number of situations, using only kinematic quantities; a framework is proposed to estimate the configuration of a manipulator using a single monocular camera; and finally, a general control framework is described which uses all of the above contributions to servo a manipulator. The results of a number of experiments are presented which demonstrate the feasibility of the proposed methods

Image-Based Visual Servoing of the I4R parallel robot without Proprioceptive Sensors

International audienc