Abstract:
The article is devoted to the approach to constructing and verification of discrete PLC-programs
by LTL-specification. This approach provides an ability of correctness analysis of PLC-programs by
the model checking method. The linear temporal logic LTL is used as a language of specification of
the program behavior. The correctness analysis of LTL-specification is automatically performed by the
symbolic model checking tool Cadence SMV.
The article demonstrates the consistency of the approach to constructing and verification of PLC
programs by LTL-specification from the point of view of Turing power. It is proved, that in accordance
with this approach for any Minsky counter machine can be built an LTL-specification, which is used for
machine implementation in any PLC programming language of standard IEC 61131-3. Minsky machines
equipollent Turing machines, and the considered approach also has Turing power.
The proof focuses on representation of a counter machine behavior in the form of a set of LTL-formulas and matching these formulas to constructions of ST and SFC languages. SFC is interesting
as a specific graphical language. ST is considered as a basic language because an implementation of a
counter machine in IL, FBD/CFC and LD languages is reduced to rewriting blocks of ST-program.
The idea of the proof is demonstrated by an example of a Minsky 3-counter machine, which implements a function of squaring.
Keywords:programmable logic controllers (PLC), construction and verification of PLC-programs, LTL-specification, Minsky counter machines.