A Modeling and Design Method for Flexible Manufacturing System Controller Software

Abstract “Entity-life modeling” (ELM) is a general method for the modeling and design of concurrent software. One area where it can applied is for the control software for flexible manufacturing systems (FMS). The application of ELM allows the integration and overall control of the operation of the numerically controlled machinery, the material transportation and storage facilities into automated factories within the context of computer integrated manufacturing (CIM). The development of flexible manufacturing has been hampered by the lack of such a general approach to FMS software design. ELM is based on the principle that processes and objects in the software are patterned after concurrent “threads of events” and objects in the problem domain. A job in an FMS represents such a thread with events such as “pick from storage”, “place on stand”, etc., which all occur sequentially and with certain time intervals. Several job threads are in progress simultaneously as different jobs are being processed. In the software, a thread of events is represented by a process, such as an Ada task. The direct coupling between the analysis and an efficient control-system software implementation is an advantage over other analysis models, such as Petri nets. A simple FMS is used as an example. It consists of a storage facility and a number of numerically controlled workstations. A conveyor belt is used for the transportation of parts between storage and workstations and between workstations.