MPC-Coder: A Dual-Knowledge Enhanced Multi-Agent System with Closed-Loop Verification for PLC Code Generation

Industrial PLC programming faces persistent difficulties: lengthy development cycles, low fault tolerance, and cross-platform incompatibility among vendors. While LLMs show promise for automated code generation, their direct application is hindered by the gap between ambiguous natural language and the strict determinism required by control logic. This paper proposes MPC-Coder, a dual-knowledge enhanced multi-agent system that addresses this gap. The system combines a structured knowledge graph that imposes hard constraints on process parameters and equipment specifications with a vector database that offers implementation references such as code templates and function blocks. These two knowledge sources form a symmetric complementary architecture. A closed-loop “generation–verification–repair” mechanism leverages formal verification tools to iteratively refine the generated code. Experiments demonstrate that MPC-Coder achieves 100% syntactic correctness and 78% functional consistency, significantly outperforming general-purpose LLMs. The results indicate that the complementary fusion of domain knowledge and closed-loop verification effectively enhances the reliability of code generation, offering a viable technical pathway for the reliable application of LLMs in industrial control systems.