Incremental modeling and verification of flexible manufacturing systems

An FMS is a typical real-time concurrent system composed of a number of computer-controlled machine tools, automated material handling and storage systems that operate as an integrated system under the control of host computer(s). The growing demand for higher performance and flexibility in these systems and the interlocking factors of concurrency, deadline-driven activities, and real-time decision making pose a significant challenge to FMS design, especially in terms of control and scheduling. A formal engineering approach that helps handle the complexity and dynamics of FMS modeling, design and analysis is needed. A Real-time Architectural Specification (RAS) model and its application in the modeling of flexible manufacturing system (FMS) are presented. RAS combines mature operational and descriptive formal methods, in particular Time Petri nets (TPN) and Real-Time Computational Tree Logic (RTCTL), to form an integrated system model for architectural specification and analysis of real-time concurrent systems such as FMS. The contribution of RAS is twofold: First, it provides a formal system to systematically maintain a strong correlation between (real-time) requirements and design and to verify the conformance of the design to the requirements, which helps enhance traceability and thus to help us to achieve high assurance in design. Second, it offers better scalability in modeling and analysis, which provides an effective way to deal with complexity in the application of formal methods. These two features together make RAS a suitable model for the design of FMS.