Design of a PLC Control Program for a Batch Plant VHS Case Study
This article reports on the systematic design and
validation of a PLC control program for the batch
plant that has been selected as a case study for the EC
project on Verification of Hybrid Systems (VHS). We
show how a correct design of the control program can
be obtained in an incremental manner using a real-time
logical formalism. This is done by systematically
strengthening the premise of an implication whose con-
clusion represents the required behaviour of the plant.
The premise specifies the assumptions under which this
behaviour is realised. The formal proof of correctness
was obtained using formal verification tools. We used
both theorem-proving (PVS) and model checking
(Spin) as verification strategies. With PVS we could
show the correctness of the final implication directly by
a semantic embedding of the real-time logic in PVS,
but only for a limited operational scenario (a single
batch load). With Spin we could show the correctness
for all relevant operational scenarios, but only indirectly,
viz. on the basis of an abstract verification model
(written in Promela). This model was obtained as a
straightforward translation of the premise of the final
version of the formal design and the PLC code derived
from it. We conclude that the judicious use of standard
formal methods and tools suffices for the systematic
development of correct control programs for this kind
of application.
A.MADER, E.BRINKSMA, H.WUPPER, N.BAUER
Reçu le 15 février 2000.
Accepté le 21 mars 2001.
Hybrid systems; Model checking; Plant control; Specification method; Theorem proving
Anglais
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