Position and Orientation Based Formation Control of Multiple Rigid Bodies with Collision Avoidance and Connectivity Maintenance

This paper addresses the problem of position- and orientation-based formation control of a class of second-order nonlinear multi-agent systems in a $3$D workspace with obstacles. More specifically, we design a decentralized control protocol such that each agent achieves a predefined geometric formation with its initial neighbors, while using local information based on a limited sensing radius. The latter implies that the proposed scheme guarantees that the initially connected agents remain always connected. In addition, by introducing certain distance constraints, we guarantee inter-agent collision avoidance as well as collision avoidance with the obstacles and the boundary of the workspace. The proposed controllers employ a novel class of potential functions and do not require a priori knowledge of the dynamical model, except for gravity-related terms. Finally, simulation results verify the validity of the proposed framework

A Cyclic Pursuit Framework for Networked Mobile Agents Based on Vector Field Approach

This paper proposes a pursuit formation control scheme for a network of double-integrator mobile agents based on a vector field approach. In a leaderless architecture, each agent pursues another one via a cyclic topology to achieve a regular polygon formation. On the other hand, the agents are exposed to a rotational vector field such that they rotate around the vector field centroid, while they keep the regular polygon formation. The main problem of existing approaches in the literature for cyclic pursuit of double-integrator multiagent systems is that under those approaches, the swarm angular velocity and centroid are not controllable based on missions and agents capabilities. However, by employing the proposed vector field approach in this paper, while keeping a regular polygon formation, the swarm angular velocity and centroid can be determined arbitrary. The obtained results can be extended to achieve elliptical formations with cyclic pursuit as well. Simulation results for a team of eight mobile agents verify the accuracy of the proposed control scheme

Distributed Control for Multiagent Consensus Motions with Nonuniform Time Delays

This paper solves control problems of agents achieving consensus motions in presence of nonuniform time delays by obtaining the maximal tolerable delay value. Two types of consensus motions are considered: the rectilinear motion and the rotational motion. Unlike former results, this paper has remarkably reduced conservativeness of the consensus conditions provided in such form: for each system, if all the nonuniform time delays are bounded by the maximal tolerable delay value which is referred to as “delay margin,” the system will achieve consensus motion; otherwise, if all the delays exceed the delay margin, the system will be unstable. When discussing the system which is intended to achieve rotational consensus motion, an expanded system whose state variables are real numbers (those of the original system are complex numbers) is introduced, and corresponding consensus condition is given also in the form of delay margin. Numerical examples are provided to illustrate the results

Consensus of Multiagent Networks with Intermittent Interaction and Directed Topology

Intermittent interaction control is introduced to solve the consensus problem for second-order multiagent networks due to the limited sensing abilities and environmental changes periodically. And, we get some sufficient conditions for the agents to reach consensus with linear protocol from the theoretical findings by using the Lyapunov control approach. Finally, the validity of the theoretical results is validated through the numerical example

Necessary and Sufficient Conditions for Circle Formations of Mobile Agents with Coupling Delay via Sampled-Data Control

A circle forming problem for a group of mobile agents governed by first-order system is investigated, where each agent can only sense the relative angular positions of its neighboring two agents with time delay and move on the one-dimensional space of a given circle. To solve this problem, a novel decentralized sampled-data control law is proposed. By combining algebraic graph theory with control theory, some necessary and sufficient conditions are established to guarantee that all the mobile agents form a pregiven circle formation asymptotically. Moreover, the ranges of the sampling period and the coupling delay are determined, respectively. Finally, the theoretical results are demonstrated by numerical simulations

An Overview of Recent Progress in the Study of Distributed Multi-agent Coordination

This article reviews some main results and progress in distributed multi-agent coordination, focusing on papers published in major control systems and robotics journals since 2006. Distributed coordination of multiple vehicles, including unmanned aerial vehicles, unmanned ground vehicles and unmanned underwater vehicles, has been a very active research subject studied extensively by the systems and control community. The recent results in this area are categorized into several directions, such as consensus, formation control, optimization, task assignment, and estimation. After the review, a short discussion section is included to summarize the existing research and to propose several promising research directions along with some open problems that are deemed important for further investigations

Estratégia de controle cooperativo baseado em consenso para um grupo multi-veículos

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2013Resumo: Nesta tese é apresentada uma proposta de controle cooperativo baseada em consenso para resolver o problema de rendezvous para um grupo multi-veículos. Como caráter essencial de cooperação os veículos, estes compartilham informação acerca do conhecimento individual, o qual está sujeito a falhas na comunicação com origem diversa, desde faltas nos dispositivos de comunicação até perdas de pacote. A estratégia de controle cooperativo proposta consiste no desenvolvimento de leis de controle descentralizadas para que cada veículo determine sua trajetória de consenso até o ponto de encontro, que a priori é desconhecido para alguns integrantes da equipe. Para tal, utiliza-se uma abordagem baseada em controle preditivo, o que permite a inclusão de requisitos de resposta, bem como de restrições, de modo a manter o caráter de cooperação entre os veículos do grupo. De forma complementar à proposta, adicionam-se à formulação das trajetórias de consenso, restrições de conectividade entre veículos, restrições de ângulo de sensoriamento em relação ao ponto de encontro e à formação de cobertura sobre o ponto de referência. Trata-se ainda neste trabalho de protocolos de comunicação com intuito de melhorar a pontualidade na troca periódica de informações, melhorando a convergência da tarefa de consenso. Abstract: In this thesis, a cooperative control strategy for teams of multiple autonomous vehicles to solve a basic coordination problem, called rendezvous problem, is presented. The vehicles share information about individual knowledge in order to cooperate. It is considered that communication failures can be occurs due to packet losses and device faults. In the cooperative proposal, a decentralized control laws are developed to drive all the vehicles to a reference position by performing trajectories with consensus. The rendezvous point is a priori unknown to some group members. The calculus of the consensus trajectories is based on receding horizon control, which allows to include response requirements and constraints for maintaining cooperation between the vehicles of the group. Additionally, it is added to the consensus trajectories formulation: connectivity constraints between vehicles, optimization of the sensing angle relative to the rendezvous point and coverage formation on the reference point. Finally, in this work, communication protocolsare studied for improving the timeliness in the information exchange, which improves the convergence of consensus task