Capacity analysis of automatic transport systems in an assembly factory

In this paper, we describe a case study concerning the capacity analysis of a completely automated transport system in a flexible assembly environment. Basically, the system is modelled as a network of queues, however, due to its complex nature, product-form network theory is not applicable. Instead, we present an aggregation/decomposition procedure, i.e. we study a number of key elements of the system in detail after which the results are implemented in the overall model for the transport system. Among these key elements are a buffer transfer system (the bottleneck of the system), modelled as a sequence of deterministic, preemptive (identical) repeat priority queues, a set of elevators, modelled as vacation servers, and several conveyor belts, modelled as pure delays (infinite servers). The numerical results appeared to be surprisingly accurate, when compared with simulation. In this short review, we focus on modelling aspects. In our view, modelling is an extremely important element of any practical application; nevertheless, the level of attention paid to modelbuilding in the literature is still limited.