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 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

Multi-vehicle consenus with target capturing and collision avoidance

International audienceIn this paper we give an analytic study to construct a command for a group of vehicles to reach a target in an hostile environment. A consensus be-tween different agents is established. This work is an extension to a previous oneEl Kamel et al.(2009) to the case of multi-vehicle. The vector which contains all the velocity fields is considered as a feedback control law. We developed a new technique which decompose the vector of velocities to a sum of two parts; an attractive part that guarantees the convergence toward the target and a re-pulsive part that ensures obstacle avoiding. Our approach is based on LaSalle's theorem. The feedback control law ensures also that each vehicle/agent choose the optimal trajectory in front of the obstacle without neither switching control nor tracking trajectory. We introduce the consensus algorithm with a constant reference state using graph theoretical tools to create an hierarchical forma-tion. The stability of the formation is realized when all agents converge to the desired configuration in neighborhood of the target

Modelling and control of a bidirectional rotors X4-flyer

International audienceThis paper presents in the first part the conception and construction of a mini 4 rotors helicopter for indoor and outdoor applications. The proposed UAV, named XSF, has a very manoeuvrable platform and is indicated to work in inaccessible spaces such as performing inspection tasks under bridges as well as inside pipes or tanks. Its main advantage with respect to classical 4 rotors helicopters is the ability of flipping two motors in order to obtain two more control inputs. This feature allows the XSF to have a better horizontal displacement or to create a yaw movement without translation. In the second part, we present a stabilization strategy around a position of equilibrium. The model is highly nonlinear, we use a methodology based on the linearization. The dynamic of the system involves six control inputs which will be computed to stabilize the engine with regard to external perturbations

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

Modélisation d'un dirigeable flexible - Modèle Eulérien

Dans cet article, nous présentons un modèle global de dirigeables flexibles autonomes subissant de grands mouvements d'ensemble et de petites déformations élastiques. Le formalisme utilisé est basé sur l'approche Newton-Euler. Dans cette étude nous développons une méthode pour généraliser les formalismes Eulériens « corps rigide » existants, en incluant l'effet de la flexibilité sans détruire la méthodologie globale. Une synthèse modale est utilisée. Une méthode hybride basée sur les principes énergétiques et les équations de Lagrange est présentée. Le phénomène des masses ajoutées est également pris en considération. Afin d'intégrer le problème d'interaction fluide-structure dans le cas du dirigeable flexible nous intégrons dans le modèle, des matrices de masses ajoutées et d'amortissement issues à la fois du mouvement d'ensemble du dirigeable et de la vibration de celui-ci dans l'air

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