Performance of a Distributed Robotic System Using Shared Communications Channels

Abstract

We have designed and built a set of miniature robots, called Scouts. In addition, we have developed a distributed software system to control them. This paper addresses the fundamental choices we made in the design of the control software, describes experimental results in a surveillance task,and analyzes the factors that affect robot performance. Space and power limitations on the Scouts severely restrict the computational power of their on-board computer, which can only handle low-level control operations and data communication on an RF data link. We use a proxy-processing scheme, in which the robots are dependent on remote computers for their computing needs. While this allows the distributed robotics system to be autonomous, the fact that the robots behaviors are executed on remote computers introduces an additional complication -- the behavior controller has to receive sensor data and send commands to the robots using RF communication channels. Because the capacity of the communication system is limited, the robots must share bandwidth. We have developed a process management/scheduling system that is capable of handling high demand when controlling a group of robots. The resource allocation system dynamically assigns resources to each robot in an attempt to maximize the utilization of the available resources while still maintaining a priori behavior priorities. We present experimental results on a surveillance task in which multiple robots patrol an area and watch for motion. We discuss how the limited communication bandwidth affects robot performance in accomplishing the task and analyze how performance depends on the number of robots that share the bandwidth.