Time-varying environment coverage control by multi-robot systems

A novel method is introduced in this paper to drive multiple robots to accomplish a given coverage task in a time-varying environment. Since a time-varying environment has a density function depending on time, its coverage problem becomes much more difficult when compared with that of a static one. To address this problem, a switching control algorithm consisting of two stages is designed to make the multi-robot system converge to a centroidal Voronoi tesselation (CVT) allocation, where the first controller successfully compensates the variation of the density function, and to avoid singularity, it is switched to the second controller when the system is close enough to the CVT allocation. As proven by Lyapunov techniques, a CVT allocation is reached as long as the density function has a decaying feature. Compared with existing results, the constructed switching controller presents the advantage that it guarantees a better allocation regardless the form of the density function. Simulation results, with density function selected as hyperbolic tangent feature or sine characteristics, are provided to illustrate the performance of the designed switching controller for the time-varying environment coverage problem.