A Tool for the Certification of PLCs based on a Coq Semantics for Sequential Function Charts

TL;DR

This paper introduces CERTPLC, a tool that certifies safety properties of PLCs described in IEC 61131-3's SFC language by generating formal certificates using Coq, enhancing industrial automation safety verification.

Contribution

The paper presents a novel framework that formalizes PLC semantics in Coq and automates the certification process for safety properties, providing independent proof certificates.

Findings

CERTPLC successfully certifies safety properties of PLCs.

The framework generates formal certificates verified in Coq.

Supports third-party validation of industrial automation safety.

Abstract

In this report we describe a tool framework for certifying properties of PLCs: CERTPLC. CERTPLC can handle PLC descriptions provided in the Sequential Function Chart (SFC) language of the IEC 61131-3 standard. It provides routines to certify properties of systems by delivering an independently checkable formal system description and proof (called certificate) for the desired properties. We focus on properties that can be described as inductive invariants. System descriptions and certificates are generated and handled using the COQ proof assistant. Our tool framework is used to provide supporting evidence for the safety of embedded systems in the industrial automation domain to third-party authorities. In this document we describe the tool framework: usage scenarios, the archi-tecture, semantics of PLCs and their realization in COQ, proof generation and the construction of certificates.