Modeling of helper robots in manufacturing systems using Petri Nets

In this paper the Timed Petri Net (TPN) is used for modeling the operations of co-operative robots in Flexible Manufacturing Systems (FMS). The effect of fault parameters and the number of co-operative robots -we call them the helpers- in the performance of the system is investigated. These special purpose robots are used to decrease the operation times, as well as to increase the total performance of the system. These robots perform the preliminary tasks on the waiting jobs (parts) in the wait lines or input buffers of machines. Also some automatic guided vehicles (AGVs) are used as material handlers between machines while performing some simple preliminary tasks during the material handling. Some sub-TPNs are used for modeling of FMS and helper robots, as special purpose robots. Simulation results show that by using the helpers, there will be a decrease of 23.7 percent in mean operation time of system, and a decrease of 25.4 percent in the mean waiting time of jobs at input buffers.