Dynamic parameters optimization of a Gough-Stewart Platform mounted on a 2-DOF moving base

International audienceA common issue of the parallel robot is that has a large number of dynamicparameters, which requires a lot of processing time, whether in dynamic modeling,identification or control. The optimization and estimation of inertial parametersof a large DoF number of robotic system is crucial to tune the model-basedcontrol law in order to improve the robot accuracy. In this paper, we present an optimizednumber of dynamic parameters, called base inertial parameters. As a result,only 90 base inertial parameters affect the evr@ simulator instead of 210 standardone. Torque signals evaluation from experimental parallel platform and the developedanalytical form show the effectiveness of the obtained results

A Strategy for Multi-Robot Navigation

International audienceThe paper addresses the problem of trajectory regulation of driftless systems such that a stabilizing control input is assumed exists. The perturbed trajectory depends on a regulation control-input which must be designed such that the system's stability is preserved and some undesirable sets belonging to navigation area must be avoided. For the stability and regulation of a multi-robot system a converging attractive set around the target is constructed and a repulsive set around obstacles is emphasized. Taking into account a communication algorithm agents-agents to agents-target, we prove that the proposed regulation control-input preserves the navigation area invariance property and the system's stability. Simulation results illustrate the effectiveness of he proposed control algorithm

Flexible Virtual Structure Consideration in Dynamic Modeling of Mobile Robots Formation

International audienceIn cooperative mobile robotics, we look for formation keeping and maintenance of a geometric configuration during movement. As a solution to these problems, the concept of a virtual structure is considered. Based on this idea, we have developed an efficient flexible virtual structure, describing the dynamic model of n vehicles in formation and where the whole formation is kept dependant. Notes that, for 2D and 3D space navigation, only a rigid virtual structure was proposed in the literature. Further, the problem was limited to a kinematic behavior of the structure. Hence, the flexible virtual structure in dynamic modeling of mobile robots formation presented in this paper, gives more capabilities to the formation to avoid obstacles in hostile environment while keeping formation and avoiding inter‐agent collision

A decentralized formation control method including self-organization around a target

International audienceThis paper presents a new strategy for formation control of multiple mobile robots to capture a target including self organization. A decentralized formation control is proposed to make the system more reliable and fault-tolerant. Acting on a hostile environnement, each robot of the formation has to avoid an obstacle. For that, we propose a new technique that modifies the trajectory behavior while preserving the formation convergence. LaSalle's theorem is applied to construct the proposed smooth continuous feedback control, to surround the target. The validity of convergence and obstacle avoidance is supported by computer simulation

CD-COCO: A Versatile Complex Distorted COCO Database for Scene-Context-Aware Computer Vision

The recent development of deep learning methods applied to vision has enabled their increasing integration into real-world applications to perform complex Computer Vision (CV) tasks. However, image acquisition conditions have a major impact on the performance of high-level image processing. A possible solution to overcome these limitations is to artificially augment the training databases or to design deep learning models that are robust to signal distortions. We opt here for the first solution by enriching the database with complex and realistic distortions which were ignored until now in the existing databases. To this end, we built a new versatile database derived from the well-known MS-COCO database to which we applied local and global photo-realistic distortions. These new local distortions are generated by considering the scene context of the images that guarantees a high level of photo-realism. Distortions are generated by exploiting the depth information of the objects in the scene as well as their semantics. This guarantees a high level of photo-realism and allows to explore real scenarios ignored in conventional databases dedicated to various CV applications. Our versatile database offers an efficient solution to improve the robustness of various CV tasks such as Object Detection (OD), scene segmentation, and distortion-type classification methods. The image database, scene classification index, and distortion generation codes are publicly available \footnote{\url{https://github.com/Aymanbegh/CD-COCO}

Co-leaders and a flexible virtual structure based formation motion control

International audienceThe motion control of multi-robots in formation using a Flexible Virtual Structure Approach (FVSA) is proposed. The dynamic model of n agents in formation is developed and sufficient conditions to the desired shape's stability over time are given. Inspired by a shepherd who supervises his troop by controlling the elements on the border, thus, he is able to control all the remainder of the troop. To control the formation shape, one defines control laws for co-leaders, selected from the border, which permits to control motions of the remaining formation agents. The strategy depend strongly on two objectives, on one hand performing an obstacles free motion and on the other avoiding collision among the agents. The Lyapunov technique is used to construct the control law ensuring obstacles avoidance for the agents on the border

Co-leaders and a flexible virtual structure based formation motion control

International audienceThe motion control of multi-robots in formation using a Flexible Virtual Structure Approach (FVSA) is proposed. The dynamic model of n agents in formation is developed and sufficient conditions to the desired shape's stability over time are given. Inspired by a shepherd who supervises his troop by controlling the elements on the border, thus, he is able to control all the remainder of the troop. To control the formation shape, one defines control laws for co-leaders, selected from the border, which permits to control motions of the remaining formation agents. The strategy depend strongly on two objectives, on one hand performing an obstacles free motion and on the other avoiding collision among the agents. The Lyapunov technique is used to construct the control law ensuring obstacles avoidance for the agents on the border

Trajectory Generation and Tracking of a Mini-Rotorcraft

International audienceWe present in this paper the stabilization (tracking) with motion planning of the six independent configurations of a mini unmanned aerial vehicle equipped with four streamlined rotors. Naturally, the yaw-dynamic can be stabilized without difficulties and independently of other motions. The remaining dynamics are linearly approximated around a small roll and pitch angles. It will be shown that the system presents a flat output that is likely to be useful in the motion generation problem. The tracking feedback controller is based on receding horizon point to point steering. The resulting controller involves the lift (collective) time derivative for what flatness and feedback linearization are used. Simulation tests are performed to progress in a region with approximatively ten-meter-buildings