Ensuring network connectivity for nonholonomic robots during rendezvous

To achieve a cooperative objective in a multi-robot system typically requires that the robots collaborate over a communication network. In this paper, we design a control strategy for repositioning and reorienting a group of wheeled robots with nonholonomic constraints and limited communication and sensing capabilities. Each robot knows the positions of only those nodes within its sensing range and can only communicate with nodes within its communication range. Thus, the objective must be accomplished while ensuring that specified nodes stay within each other's sensing and communication ranges and that the overall communication network stays connected. To achieve these objectives, we develop a dipolar navigation function and corresponding time-varying continuous controller. We show that if the network is initially connected, the controller maintains the specified communication links at all times while moving the robots into the specified positions and orientations. We consider the particular application of moving the robots to a common rendezvous point with a specified orientation. Simulation results verify the effectiveness of the proposed approach.