Consensus of self-driven agents with avoidance of collisions
  In recent years, many efforts have been addressed on collision avoidance of collectively moving agents. In this paper, we propose a modified version of the Vicsek model with adaptive speed, which can guarantee the absence of collisions. However, this strategy leads to an aggregated state with slowly moving agents. We therefore further introduce a certain repulsion, which results in both faster consensus and longer safe distance among agents, and thus provides a powerful mechanism for collective motions in biological and technological multi-agent systems. 
Liqian Peng, Yang Zhao, Baomei Tian, Jue Zhang, Bing-Hong Wang,   Hai-Tao Zhang, and Tao Zhou