Performance analysis of token bus LAN in coordinating multiple robots

Using a local area network (LAN) to coordinate multiple industrial robots is considered in this paper. The LAN uses the standard Manufacturing Automation Protocol (MAP) to control the access of the communication bus. Since the MAP based LAN was not designed for real-time applications, performance evaluation of the LAN becomes an important issue. A new evaluation method is proposed in this paper. The method evaluates the efficiency of the LAN by a parameter called effective token passing ratio. This parameter is affected by the speed and the access protocol of the LAN as well as the task decomposition-and-allocation scheme for computing the coordination algorithms. Previous methods, however, only evaluate the speed and the access protocol of the LAN. As a result, the new method provides more options for improving the LAN based system. To guarantee real-time coordination of multiple robots, the lower bound of the effective token passing ratio is determined and the probability of successful coordination when the transmission errors are possible is also considered