Model-Based Design of PLC Programs

Programmable logic controllers (PLC) have been one of the important players in manufacturing systems and many other applications with sales of 15 million PLCs worldwide every year. However, our research has revealed that the programming of PLC based control systems is still very much relying on trial-and-error. In addition, current PLC based control systems are not properly designed to support the growing demand for flexibility and reconfigurability of manufacturing systems. This paper will report a systematic approach to model and design PLC based control systems for reducing the uncertainties in managing the control software development, increasing the flexibility of the systems, and facilitating the use of simulation technology for systems validation. This approach involves systematic design principles, formal modeling techniques, and a generic software component library structure. An example of using the proposed approach is given to illustrate the design of PLC based control systems for a material handling systems.