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This work presents a strategy to guide an n-robot convoy in a rigid virtual structure, split into n −2 triangular formations. Each set of three robots represents one formation, and transformation functions relate the robots' position to the formation's pose and shape, and vice versa. Each triangular formation has its own constructive sequence (clockwise or counterclockwise), which depends on the robots' position, and is crucial for the control navigation. As first contribution, we propose a strategy based on cross-product concept to identify automatically the current and the desired triangle sequence. Furthermore, once knowing each robot can belong up to three formations, our second contribution is a control signals weighting, to improve simultaneous convergence of the whole formation. Finally, we present real experiments with four Pioneer-3DX robots performing a trajectory tracking task to validate our proposal.

This work presents a strategy based on vector fields to guide a group of aerial robots in order to converge and circulate a closed and time-varying curve in the three-dimensional space. A set of modulation functions, that prevents collisions between robots by setting priorities, acts on controllers based on artificial vector fields, considering a decentralized architecture. In addition, it is proposed an extension of the backstepping controller with integral action for the low level control of each quadrotor. This extension, based on the Lyapunov Redesign technique, makes the system robust for bounded disturbances. Simulation results show the effectiveness of the strategy adopted. Resumo: Este trabalho apresenta uma estratégia baseada em campos vetoriais para guiar um conjunto de robôs aéreos de forma a convergir e circular uma curva fechada e variante no tempo no espaço tridimensional. Um conjunto de funções de modulação, que evita colisões entre os robôs por meio da definição de prioridades, atua sobre controladores baseados em campos vetoriais artificiais, considerando uma arquitetura descentralizada. Além disso, propõe-se uma extensão do controlador backstepping com ação integral para o controle de baixo nível de cada veículo quadrotor. Esta extensão, baseada na técnica Lyapunov Redesign, torna o sistema robusto frente a distúrbios limitados. Resultados de simulação mostram a eficácia da estratégia adotada.

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