Scheduling and optimization for a class of multi-stage hybrid manufacturing systems

In this paper, a study on modeling, scheduling and optimal control problems for a class of hybrid multistage manufacturing systems is investigated. In this framework, the discrete entities have a state characterized by a temporal component whose evolution is described by event-driven dynamics and a physical component whose evolution is described by continuous time-driven dynamics, thus it is a typical hybrid system. Not only the optimal control for manufacturing process like that discussed in many references but also the optimal machining sequence on each machine are considered in this paper. The whole problem is solved by a two-level optimization method: in the inner level, for any given job processing time sequence of all jobs, the optimal machining sequence is considered, which is a typical discrete combinatorial optimization problem in general case, so the difficulty is increasing rapidly with the increase of job and machine numbers; while at the outer level, we use an improved evolutionary programming algorithm to decide the optimal control for each job in each stage of the process. Finally, some examples are given to illustrate the validity of our algorithm