Automated Cross-Platform PLC Code Translation and Real Equipment Validation Using Large Language Models

This study proposes a web-based system that automatically converts LSIS PLC programs written in IL into Siemens STL using a large language model (Gemini API). The system consists of a JavaScript frontend and a FastAPI backend, with components for prompt design, I/O mapping, and output postprocessing. Five pneumatic control scenarios were tested using real Siemens S7-1500 hardware, and the converted STL programs executed correctly in all cases, requiring only minor edits. The results demonstrate the feasibility of LLM-based PLC code translation and suggest potential for future extensions to multiple brands and advanced functions.