Client server-based distributed architecture for
concurrent design of DCS networks: a case study
N.G.P.C. Mahalik
Department of Mechatronics, Kwangju Institute of Science and Technology, Korea
S.K. Lee
Department of Mechatronics, Kwangju Institute of Science and Technology, Korea
Introduction and background
Trends
Next generation manufacturing,
instrumentation and process control
environment require more sophistication,
flexibility and smartness in response to the
need for high productivity (Bauer, 1995; Reza,
1994). Tremendous advances in the field of
digital communication, semiconductor
technology and the idea of distributed parallel
processing have triggered the researchers,
developers, control engineers and system
integrators to formulate the specification of
requirements for the design of flexible
distributed architecture for industrial control
solutions (Armstrong and Moore, 1994).
Reconfiguration, condition monitoring and
maintenance (Evans, 1995), SCADA
(supervisory control and data acquisition)
implementation (Brinkler et al.,1997),FDI
(fault detection and isolation) (Lautala et al.,
1996) solution, component validation (CmV)
and life cycle data acquisition (LCDA)
(Mahalik, 1998), etc. are considered to be few
parameters of the term flexibility.
Digital control networking systems
Traditional control schemes are centralised
in nature. That is the interaction between the
field devices such as sensors, actuators,
valves, drives, switches etc. is governed by
only one central computer. Centralised
configurations have their inherent problems,
such as:
1 future modification requires the entire
control system to be shut down;
2 not adaptive;
3 high installation cost because of one-to-
one correspondence between the field
devices and the central controller; and
4 the system becomes paralysed if the
central computer fails to operate.
Distributed Control System (DCS) based
solutions overcome these problems to a large
extent (Mahalik and Moore, 1997; Pu and
Moore, 1995).
In considering the advancements mentioned
in the previous section, the trend is now to
implement distributed control schemes using
digital control networking systems (i.e.
fieldbus) within the manufacturing,
instrumentation and process control
environments. A fundamental enabling
technology in realising intelligent and
responsive manufacturing is that of
distributed real-time control, sometimes
referred to as fieldbus technology (Wood, 1995;
Foster et al., 1995). Fieldbus technology enables
intelligence to be distributed to the device
level in such a way that improved monitoring
and control would be possible. Fieldbus is a
standard for digital communication at the
plant floor level for automation systems and
could offer the most robust and future-proof
route into the technology.
Most large process control equipment
vendors are developing proprietary digital
data bus schemes for their target markets.
Unfortunately many of the devices, made to
the different proprietary designs, could not
be interconnected to a common data bus
without the development of suitable
hardware and software interface. However,
the requirements of the multi-national user
companies led to demands for a single
internationally recognised standard. In
response to this, the International
Electrotechnical Commission (IEC) started
the IEC Fieldbus project to develop a single
standard to support all digital data signaling
requirements for plant-wide process control
applications (Pinto, 1995). But the
standardisation work has not yet been
finished. With internationally agreed
standards in terms of interoperability and
interchangeability yet to be finalised we can
find many fieldbus vendors and suppliers in
the technology marketplace. Out of these the
standard protocols are, LonWorks
The current issue and full text archive of this journal is available
at
http://www.emeraldinsight.com/0957-6061.htm
[47]
Integrated Manufacturing
Systems
13/1 [
2002
]47±57
# MCB UP Limited
[
ISSN 0957-6061
]
[
DOI 10.1108/09576060210411503
]
Keywords
Network management tool,
Control network, Client server,
Fieldbus,
Computer integrated manufacturing
Abstract
Traditional network management
tools (NMT) are centralised in nature,
as a result of which they are not
flexible enough when large control
network (e.g. SCADA network)
design is desired for. In this paper
conventional NMTs have been
segmented into components with
unified and dedicated functions.
Each component has been
configured as a client with regard to
a central database (i.e. server). The
components co-operate with other
components. The work includes the
design of flexible NMTs in terms of
advanced software architecture for
the management of control
networks. Three software
components (Installation,
Configuration and Testing) based on
CS architecture and object-oriented
philosophy have been developed. The
components are realised with LON
2
(Local Operating Network) platform;
a proprietary fieldbus system from
Echelon, Microsoft's Visual Basic-4
platform and Microsoft's Windows98
operating system. LON Component
Architecture Object Server (LCAOS)
serves as the network kernel in this
design. The configurable components
can be used concurrently for the
design of control networks.
Received October 1997
Revised October 2000
Accepted February 2001