Exploration of a minimum tardiness dispatching priority for a flexible manufacturing system - a combined simulation / optimization approach

This paper presents a simulation-optimization approach to find an appropriate dispatching priority. The study is based on a detailed simulator for a module-type commercial FMS. Specifically, after presenting the basic configuration and fundamental control logic of the system together with its main characteristics as a special type of a job shop, an algorithm is presented which combines simulated annealing and simulation to explore a dispatching priority of operations that minimizes the total tardiness. Computational performance of the algorithm is presented which shows that good solutions can be obtained mostly after 300 iterations or so. The paper also compares the performance of the 'optimal' or near optimal dispatching priority generated by the proposed algorithm with those generated by standard dispatching rules. The results show that standard dispatching rules such as EDD and SLACK which take due dates into considerations perform moderately, but not extremely well. The results also show that some of the workload-based dispatching rules such as SPT work consistently well.