Abstract
Timed Petri-net (TPN) models were developed for evaluating the performance of robot-centred manufacturing cells (RMCs) by analysing interactions between the robot and workstations in the cells. The performance measures evaluated were average resource utilisations, average queue lengths, and average production rates. RMCs have been classified for the purpose of modularity into three types: parallel-type, flow-type and multiproduct-type. A modular approach which facilitates an easy model construction was used for constructing TPN models for these types of RMCs. Structural analysis ensured that parallel-type and flow-type RMCs possessed properties of boundedness (finite states) and liveness (recurrence) both of which would guarantee that the equivalent Markov chain is ergodic, that is, the limiting probabilities exist. Liveness of multiproduct-type RMC, however, cannot be ensured since deadlock could exist in such a cell. This situation is discussed. Generalized timed Petri-net analyser (GTPNA) was used to support the evaluation of the TPN models obtained. © 1994 Springer-Verlag London Limited.