Performance analysis of token bus LAN in coordinating multiple robots

Using a local area network (LAN) to coordinate multiple industrial robots in a multirobot system (workcell) is studied. The properties of the multiple robot coordination task are first discussed. Then, a method is proposed to evaluate a pre-defined task decomposition and allocation scheme for the coordination task. In this method, a parameter called effective token passing ratio (ETPR) is defined to measure how efficient the scheme is when the token bus LAN is used as the communication medium. A lower bound of the ETPR is analytically determined based on time constraints imposed on the task. By using this method, one does not need to determine the communication delay and computation time of individual tasks (or subtasks) decomposed from the coordination task. Instead, one can compare the ETPR of the network with the lower bound. From the comparison, it can be determined whether the task decomposition and allocation scheme is appropriate. The probability that real-time coordination is successful is also computed