سیاست های سوئیچینگ مناسب برای برنامه ریزی FMS

Switching server, otherwise known as hybrid dynamical approaches can be used highly effectively to solve flexible manufacturing systems scheduling problems. Papers published in this field have accepted that the demand rates determining the production tasks have some given values. In the present paper it is shown that the demand rates should be selected from some given domains. The “control variables” to realize suitable processes are the switching policies, and the demand rates. These uniquely determine the processes through the switching time sequences. In the present paper, two variants: the single machine processing, and the multiple machine processing cases are analyzed. It is very problematic to use continuously coupled parts flows for stable and effective production. To eliminate this difficulty, in the present paper, the method called controlled buffer technique is proposed, which uses the opportunity that the computer controlled “virtual buffers” can be filled up before the regular working time, and used for part flow compensation.

Manufacturing automation is highly connected with the use of CNC machine tools, robots and other mechatronic devices. These and the information processing subsystems are integrated into flexible systems of different type. Flexible manufacturing systems are ones of the most importants from those. One of the most important tasks of the production planning subsystem on this level is the scheduling. Recently, methods have been proposed for solving flexible manufacturing system (FMS) scheduling problems, using hybrid dynamical approach. These give an opportunity to significantly increase the effectiveness of work organization of these high value systems. Scheduling problems in manufacturing industry have been frequently solved by heuristic methods. A developed form is, when these are based on priority rules. If a priority rule is given, it fully determines the schedules. Of course, the scheduling algorithms may also contain the combination of different rules, taking into consideration not only the priority indices values, but other factors, too. The schedules are usually given by GANTT diagrams, or by the corresponding tables.

Let us give a short overview of the results outlined in the present paper. It was shown how the demand rates domains for single machine and multiple machine production can be determined. Instead of (more exactly, together with) infinite time approaches, a finite time horizon was supposed, suitability and practical suitability conditions were formulated. These give a real practical opportunity for system synthesis. But the problem should be solved how to provide constant demand rates at consecutive machine groups. This can be solved by using the controlled buffer technique proposed in this paper. Let us indicate some problems which stay open for the use of hybrid dynamical approach to FMS scheduling. It is not clear where the borders of using of methods based on this approach are. That is, what does “high number of parts” mean. FMSs are very effective in one of a kind, or small series production. For these, the classic approaches give suitable results. Where does the new approaches field begin? The use of controlled buffer technique seems to solve difficult problems. The open question is how the initial buffer contents needs change the production situations? Because these should be provided to several machine groups, the total content could be high. Of course, if the number of parts is high enough, this fact may not be a hard problem. But, in other cases it might.