Planning in virtual enterprises using the NETSIM approach

Summary form only given. To ensure their competitiveness SMEs (small and medium sized enterprises) have to take up completely new challenges concerning their participation in dynamic networks and virtual factories. A number of powerful software systems are available for most of the tasks. However, all these systems are not systematically integrated so that they do not form a homogeneous platform for the SME user. With our NETSIM concept (network simulation) we want to contribute to finding a way out of that situation. Its basic idea is to provide a stochastic interpretation of deterministic networks as they are managed by traditional PPC-systems, i.e. the duration of work units, transportation times, influence factors, availability of material and human resources etc. are modeled as probability distributions. This will enable, among others, a (virtual) manufacturer to consider and exploit deviations that might occur during production in order to detect and implement an optimal solution for a given planning task. A particular step of this approach is the automatic extraction and transformation of PPC's networks into a simulation model in the format that is expected by a simulation tool. The simulation results then are fed back into the PPC system, i.e., NETSIM proposes: to take the PPC network as a basis for a simulation model; to replace the constant parameters of a network by suitable distributions, thus reflecting the in-determinism of influence factors in manufacturing; and to extend the network by alternative process sequences decision points.