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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
A Control Flow based Static Analysis of GRAFCET using Abstract Interpretation
The graphical modeling language GRAFCET is used as a formal specification
language in industrial control design. This paper proposes a static analysis
approach based on the control flow of GRAFCET using abstract interpretation to
allow verification on specification level. GRAFCET has different elements
leading to concurrent behavior, which in general results in a large state
space. To get precise results and reduce the state space, we propose an
analysis suitable for GRAFCET instances without concurrent behavior. We point
out how to check for the absence of concurrency and present a flow-sensitive
analysis for these GRAFCET instances. The proposed approach is evaluated on an
industrial-sized example.Comment: \c{opyright} 2023 IEEE. Personal use of this material is permitted.
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Structural Synthesis for GXW Specifications
We define the GXW fragment of linear temporal logic (LTL) as the basis for
synthesizing embedded control software for safety-critical applications. Since
GXW includes the use of a weak-until operator we are able to specify a number
of diverse programmable logic control (PLC) problems, which we have compiled
from industrial training sets. For GXW controller specifications, we develop a
novel approach for synthesizing a set of synchronously communicating
actor-based controllers. This synthesis algorithm proceeds by means of
recursing over the structure of GXW specifications, and generates a set of
dedicated and synchronously communicating sub-controllers according to the
formula structure. In a subsequent step, 2QBF constraint solving identifies and
tries to resolve potential conflicts between individual GXW specifications.
This structural approach to GXW synthesis supports traceability between
requirements and the generated control code as mandated by certification
regimes for safety-critical software. Synthesis for GXW specifications is in
PSPACE compared to 2EXPTIME-completeness of full-fledged LTL synthesis. Indeed
our experimental results suggest that GXW synthesis scales well to
industrial-sized control synthesis problems with 20 input and output ports and
beyond.Comment: The long (including appendix) version being reviewed by CAV'16
program committee. Compared to the submitted version, one author (out of her
wish) is moved to the Acknowledgement. (v2) Corrected typos. (v3) Add an
additional remark over environment assumption and easy corner case
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