Automatic translation from FBD-PLC-programs to NuSMV for model checking safety-critical control systems

Programmable logic controllers (PLCs) are digital control systems, commonly used in industrial automation and safety-critical applications. Control systems used in safety-critical areas must undergo an extensive and thorough certification and verification process. In safety-critical applications, the PLC programming standard IEC 61131-3 is widely accepted in industry. PLC programmers who develop control systems for safety-critical systems are often required to verify the logic of PLCs by using formal methods such as model checking. Translating manually from a PLC program to the input language of a model checker takes times and is often error-prone. We develop a compiler to automatically translate PLC programs in the function block diagram (FBD) language, one of five industry standard PLC programming notations, to the input language of the model checker NuSMV. We have evaluated correctness, robustness, and performance of the PLC-NuSMV compiler using a case study. Evaluation results show that the compiler can translate the PLC programs correctly. The compiler can also identify several input errors and can scale to relative large PLC programs