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In this paper, we aim to extend our approach to automatically generate simulations
to cover and facilitate the development of interlocking functions. We present a mod-
elling framework supporting the modelling of the functionality of interlocks and how a
simulation model of a controlled system can be created using model-based techniques.
The paper also discusses the relationship between safety functions and interlocks with
the purpose of assessing whether also the development of critical safety functions could
be based on modelling and simulations. For defining interlocks, we do not suggest any
new modelling notation. Instead, we integrate a commonly used notation to our model-
based approach. The novelty of the approach is, thus, not in the way of specifying
the interlocks but in the way in which simulations are integrated to model-based inter-
lock development and how the simulation models can be created based on early design
models.
This paper is organized as follows. Section 2 reviews work related to use of sim-
ulations and model-based development in industrial control and automation domain.
Sections 3 and 4 present a more detailed introduction to interlocking functions, our ap-
proach to simulation-assisted development of interlocks and the developed tool support,
respectively. Section 5 presents an example modelling project in which the approach
and tools are utilized. Finally, before concluding the paper, section 6 discusses whether
model-based, simulation assisted development techniques could be used in development
of actual safety functions and to reveal security-related problems.
2
Related Work
Simulations can facilitate the development of manufacturing processes, machines and
plants as well as automation and control systems in several ways. For example, Karhela
in [9] mentions the use of simulations to control system testing, operator training, plant
operation optimisation, process reliability and safety studies, improving processes, ver-
ifying control schemes and strategies, and start-up and shutdown analyses.
In [3] the author compares the I/O simulation approach to the traditional approach
of performing system testing only on-site with the actual processes. According to the
paper, the use of simulations may result in shorter start-up times as well as less waste
of end products during the start-ups. In addition, simulations enable better operator
training, ability to test control programs in smaller modules, and the ability to thorough
testing of emergency and dangerous situations. [3]
A more recent survey on use of simulations in industrial control domain was made by
Carrasco and Dormido in 2006 [2]. According to the paper, the benefits of using control
systems in simulators before installation include improvements to 1) design, develop-
ment and validation of the control programs and strategies, 2) design, development and
validation of the HMI (human-machine Interface) and 3) adjustments of control loops
and programs. [2] It is thus evident that simulations may facilitate both the develop-
ment and commissioning of control systems. Simulation solutions are nowadays also
provided by major control system vendors as listed in [2].
The goal of our approach is to enable automated utilization of design-time models
of control systems and applications so that, for example, early simulated testing of a
control or interlocking approach would not need the actual control system hardware
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