Discrete event simulation for supporting production planning and scheduling decisions in digital factories

The paper tackles the problem of managing uncertainties during the execution of predictive schedules in a dynamic environment. The dynamic environment in question is represented by a simulation model which constitutes a coherent part of a Digital Factory solution. The model is connected to an integrated production planner and job-shop scheduler system with flexible modelling capabilities and powerful, scalable solution methods. The paper addresses the simulation module of the architecture highlighting its main functionalities. The paper also shows the potential of using the simulation model in two different ways. Both applications support the production planning and scheduling decision making process, but from two different viewpoints. On the one hand, the model presented in the paper can be applied as a schedule evaluator, on the other, it can serve as a simulation-based scheduler as well. A brief description about possible schedule evaluation criteria is also provided. Within the integrated hierarchical architecture the schedules are calculated by a constraint-based deterministic scheduling algorithm. Results of experiments which were achieved by using the model of a real, large job-shop environment are also provided.