Runtime Enforcement of CPS against Signal Temporal Logic

TL;DR

This paper introduces a method for runtime enforcement of Signal Temporal Logic properties in Cyber-Physical Systems, translating STL formulas into timed transducers to minimally modify signals and ensure safety guarantees.

Contribution

It develops a novel approach translating STL formulas into timed transducers for runtime enforcement in CPS, addressing hybrid dynamics not handled by previous methods.

Findings

Effective enforcement of STL properties demonstrated in a case study

Timed transducers for 'until' and 'release' operators enable enforcement

Empirical evidence supports suitability for CPS applications

Abstract

Cyber-Physical Systems (CPSs), especially those involving autonomy, need guarantees of their safety. Runtime Enforcement (RE) is a lightweight method to formally ensure that some specified properties are satisfied over the executions of the system. Hence, there is recent interest in the RE of CPS. However, existing methods are not designed to tackle specifications suitable for the hybrid dynamics of CPS. With this in mind, we develop runtime enforcement of CPS using properties defined in Signal Temporal Logic (STL). In this work, we aim to construct a runtime enforcer for a given STL formula to minimally modify a signal to satisfy the formula. To achieve this, the STL formula to be enforced is first translated into a timed transducer, while the signal to be corrected is encoded as timed words. We provide timed transducers for the temporal operators \emph{until} and \emph{release} noting that other temporal operators can be expressed using these two. Our approach enables effective enforcement of STL properties for CPS. A case study is provided to illustrate the approach and generate empirical evidence of its suitability for CPS.