Maintaining Communication Link for Tactical Ground Robots

The communication link between a tactical mobile robot and its control station is currently the Achilles’ heel of any ground robotic operation in the field. High-bandwidth digital radios, while providing the robot greater mobility than tethered links, perform mostly on lines of sight. The communication link degrades quickly as a robot penetrates the interior of a building, tunnel, or cave, or is shielded by intervening structures. We have demonstrated a solution to this problem through the use of autonomous mobile relay nodes. Each node is a small robot carrying a high-bandwidth digital radio. The relay robots convoy behind the main robot at the start of a mission, and automatically stop where needed to form an ad hoc network guaranteeing a link between the lead robot and the base station. This is accomplished without the need for an operator’s intervention. The relay robots’ mobility allows for even more versatility in the network. At any instance, nodes that are not needed in the network have the ability to request a map that has been generated by the lead robot as it moves through the environment, and use it to rejoin the convoy, further extending the lead robot’s range. This paper describes the system, strategy, hardware development, software algorithms, and experiments conducted. It also briefly describes a follow-on project that demonstrates automatic deployment of static relay bricks by the lead robot.