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Virtual Factory Integrated Manufacturing System for Process Simulation and
Monitoring
Zewei Zhou, Yiping Feng, Gang Rong*, Feng Zhu
*State Key Laboratory of Industrial Control Technology, Institute of Cyber-Systems and Control,
Zhejiang University, Hangzhou, 310027, P.R.China (e-mail: grong@ iipc.zju.edu.cn)
Abstract: A virtual factory integrated manufacturing system combined with system simulation and virtual reality is
introduced in this paper. We describe the system architecture and development methodology, provide the working
principle of process simulation and monitoring in virtual factory, and then explain the detailed applications of virtual
factory integrated manufacturing system. With the visualization and three-dimensional human-computer interaction
about process and production data, this platform can provide effective supports on monitoring, control and operation of
manufacturing system.
Keywords: simulation; integration; virtual reality; intelligent manufacturing systems; integrated plant control
1. INTRODUCTION
Virtual reality combined with process simulation and
monitoring is one of the attractive research topics in process
industry. Virtual reality is a computer system which can
create a virtual world, and provide users with the feel as they
were right on the scene. Virtual reality system generally has
three features (Bridge et al., 2007): immersion, interaction,
imagination. Users can wander in the virtual reality
environment (Mujber et al., 2004), think and analyze the
information perceived, emerge those wanted strategy, then
provide feedback to the system to interact with the system
and control its process. Since performing experiments on
industrial equipments may be expensive and risky, research
in the virtual manufacturing system will be very important.
CB&I Company in Chicago (USA) had developed the 3D
Virtual Refinery and provided intuitive description of
material flow in refinery. (Fang et al., 2006) introduced a
detailed analysis of the development of dynamic-static
hybrid simulation platform and combined dynamic
simulation of key units with static simulation of the whole
industrial process in the virtual factory laboratory system.
(Wu et al., 2006) proposed a virtual factory framework
which integrated enterprise-level operation and process
simulation.
In this paper, we introduce a virtual factory integrated
platform, and explain its overall design and architecture.
With the combination of system simulation and virtual reality,
the virtual factory integrated platform realizes the
visualization of both process simulation results and process
data and provides effective supports on decision making for
process simulation and monitoring in the manufacturing
industry.
2. SYSTEM ARCHITECTURE AND DEVELOPMENT
METHODOLOGY
Virtual factory integrated platform is composed of a database
system, a dynamic-static simulation system, and a
three-dimensional scene system. Each subsystem can
communicate information with others to realize the
integration of total platform. According to virtual reality
modelling language (VRML) (Ieronutti et al., 2007), we use
Autodesk 3ds Max tool to build the three-dimensional
models in virtual factory, and use Microsoft Visual Studio C#
Preprints of the 18th IFAC World CongressMilano (Italy) August 28 - September 2, 2011
Copyright by theInternational Federation of Automatic Control (IFAC)
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program language to integrate those models to create a
virtual environment. Similarly to the human-computer
interface mentioned in the reference (Sun et al., 2009), we
build a three-dimensional input-interface through which
users can set different instructions about scheduling and
process control in virtual factory, then put these control
parameters into the integrated database system. Meanwhile,
dynamic-static simulation system obtains these instructions
and runs corresponding simulation models. Then the
simulation outputs are saved into the database system.
Finally three-dimensional scene system reads these data and
visualizes the simulated process of production in the virtual
environment, which can augment reality (Reif et al., 2008).
And the closed loop simulation architecture about the
process simulation of virtual factory integrated platform is
illustrated as Fig.1, which shows the system principle.
Database system describes the topological structure of
simulation models with a series of static data tables,
including different devices, units, pipes, streams along with
their properties and relationship, and also describes the
instructions and simulation result with a series of dynamic
data tables. Dynamic-static simulation system is based on
mechanistic models and production data, which can realize
the production changing process and support for process
control system in virtual factory (Mert et al., 2009). And the
three-dimensional scene system realizes human-computer
interaction and information representation (Soares et al.,
2004). In order to show sufficiently the layout of each
equipment workshop, the overall design of virtual factory is
very important and its 3D scene model is constructed, which
can make best satisfaction for users. Therefore, we refer
some design standards in petroleum and petrochemical
industry, including design specification for site plan in
petrochemical engineering and general rule of plant layout
design for petrochemical industry. Then we design a virtual
factory as shown in Fig.2, which is quite similar to a real
factory. In order to realize such a virtual factory integrated
manufacturing system, the connection and interaction of
information flow among these subsystems is very important,
which integrates all the modules as a whole.
3. WORKING PRINCIPLE OF VIRTUAL FACTORY
Process simulation and monitoring platform in virtual factory
can realize multi-level simulation among different business
levels, especially in process control system level and
manufacturing executive system level. The working principle
and system structure is illustrated as in Fig.3. The objective
of the virtual factory platform is to construct a
three-dimensional human-computer interface not only for
manipulation of simulation process, but also for monitoring,
control and decision making for the real-time manufacturing
system.
Fig.1. Closed Loop Simulation Architecture of Virtual Factory Integrated Platform
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Fig.2. Virtual Factory Three-Dimensional Integrated
Manufacturing System
As an integrated platform, each subsystem has its own
structure and connects with others in the form of process
data and operational instructions. Dynamic-static hybrid
simulation system consists of some simulation modules of
production process, such as dynamic simulation of unit
operations and static simulation of material flow and energy
consuming. The simulation models are integrated and
manipulated with the interactive control interface. And the
simulation result data are transmitted into the integrated
database platform, which consists of basic description
property data about factory models, process interactive
control parameter tables and simulation result statistics data
tables. Meanwhile there is an aggregation from real time
database (RTDB) to relational database Oracle for the
multi-level integrated simulation in virtual factory.
Visualization process monitoring platform is designed both
for simulation process and real-time production data. The
process parameters in Fig.3 represent process measurements
such as temperature and flowrate, which are visualized with
3D measurement instruments and control valve in the
platform. Since the virtual factory is constructed according to
the industrial field of real factory, visualization monitoring
platform is quite the same as that in industry field.
The procedure diagram for constructing virtual factory
simulation platform is shown in Fig.3. Firstly, we analyze
and design the virtual factory layout, including plant-wide
layout and workshop layout.
Fig.3. Process Simulation and Monitoring in Virtual Factory Integrated Platform
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Then we build 3D models about virtual factory devices to
create an interactive 3D virtual factory dynamically and use
the texture mapping technology to realize dynamic-static
process simulation for augmenting reality. And then we
present the varying production process information to create
man-machine interaction environment for interactive control.
Process monitoring system which consists of process
monitoring and fault simulation can also transmit
information to integrated database platform and interact with
virtual factory simulation platform. Finally there is some
feedback information from virtual factory simulation
platform, which can improve simulation and control effects
by modifying some control parameters.
4. APPLICATIONS OF VIRTUAL FACTORY
4.1 Dynamic-Static Hybrid Process Simulation
In the virtual factory integrated platform, dynamic-static
hybrid process models describe the input-output relational
mechanism about process units, which can simulate the real
process of the factory. When the production plan or the
scheduling instruction changes, the simulation platform
would calculate the response and output of the production
process and generate a series of production data for further
research of the real process.
We take Fluid Catalytic Cracking Unit (FCCU) in the virtual
refinery for example. Firstly, three-dimensional models of
reactors, regenerators, measuring instruments and control
valves are established. Then the dynamic mechanistic models
of FCCU are built up to implement dynamic simulation. In
the human-computer interface, operators can set control
parameters and introduce different disturbances, such as
change of yield, change of oxygen content in regenerators,
change of level and pressure in reactors. Dynamic simulation
program get these instruction parameters and start to
simulate, then put result into database again. Finally the
three-dimensional scene system reads these production data
and represents the varying process states of FCCU in a 3D
interactive way. We make the reactant bubbles rise or fall
according to the production data, which represents the
change of level in reactors or regenerators. The color of inner
space of reactors or regenerators will change continuously
according to the temperature or pressure data, and the
different degree of color represents the different numerical
value of temperature or pressure. The flowsheet of FCCU
simulation system is illustrated as in Fig.4.
Fig.4. Process Flowsheet of FCCU Simulation Model
Visualization and representation of dynamic simulation of
FCCU is illustrated as Fig.5, which shows representation of
temperature, and the different degree of red color means
different degree of temperature. When the temperature of
reactors is higher, the degree of red color is deeper. And
when the mouse on the interactive interface clicks the
position of a measuring instrument, the pointer and digital
data on the panel shows the corresponding instrument
information. Fig.5 can also show monitor screen of control
valve, and the pointer and digital data on the panel shows
real-time opening information of the control valve which is
clicked. Based on the simulation models and data, we can
help operators and engineers in refinery to be familiar with
the flowsheet and process control system of FCCU, and also
provide a visualization monitoring platform for real-time
production.
Simulation and visualization of the process of coal pyrolysis,
the second example of virtual factory, is shown in Fig.6,
which can simulate the process of how coal is decomposed
to produce acetylene. Fig.6 (a), (b) show the global layout of
the coal pyrolysis process, and Fig.6 (c), (d) show the
specific coal particle simulation process.
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Fig.5. Dynamic Simulation of FCCU in Virtual Factory
Fig.6. 3D Simulation of Coal Pyrolysis in Virtual Factory
Visualization and interaction make virtual factory simulation
platform provide effective support for process simulation and
real-time monitoring. Dynamic-static simulation can solve
many practical problems, such as setting control parameter
according to different disturbances, selecting production
schemes, and analyzing or predicting variation trend of
process plant. Without going to the real factory, users can
wander around the process units, and operate those
instruments and valves to see the response of control and
real-time production information, which is useful for their
decision making.
4.2 Process Fault Visualization
Safe and stable environment in manufacturing industry is
very important. It is necessary to monitor and identify the
abnormal changes in process variables both in virtual factory
and real world. Process monitoring in the virtual factory
helps users detect and analyze the causes of fault, and to be
similar with fault that not happen in the real factory. At first,
we build fault simulation models and generate process data
with fault about processing units, which are based on process
conditions, status of measuring points and in-out flow. Then
the consequence of the given fault and the procedure of
eliminating the fault will be visualized. We can take oil
spilling out from tower top as an example. Because the valve
of outlet was plugged, the level of material in the tower was
rising. When the oil reached the top of tower, it spilled out,
as illustrated in Fig.7. In order to eliminate fault, operators
turned off the valve of incoming line, and turned on the
valve of outlet, so the level will fall down until coming back
to normal.
Fig.7. Process Fault Visualization in Virtual Factory
Visualization and interaction help operators get a deep
impression and make timely decision to create a safe and
stable environment in virtual factory.
4.3 Process Monitoring in Virtual Factory
Virtual factory integrated platform can be applied in many
different industries, such as oil refinery and coal chemistry
plant. Fig.8 shows the visualization monitoring platform of
Flow Measuring Instrument Temperature Measuring Instrument Control Regulating Valve
Pressure Measuring Instrument Level Measuring Instrument Visualization Monitoring I
Visualization Monitoring II Visualization Monitoring III Visualization Monitoring IV Fig.8. Visualization of Coal Pyrolysis to Acetylene
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coal pyrolysis to produce acetylene by using hydrogen
plasma, including measuring instruments, control valve, and
the pointers and digital data on the panels that visualize the
varying process of real-time production. 3D visualization
monitoring makes users be familiar with the production
process more intuitively, which is quite different from 2D
monitoring. The virtual factory has been used for operators
training of coal pyrolysis process.
5. CONCLUSIONS
The virtual factory integrated manufacturing system provides
effective support for 3D process simulation and monitoring,
with the interaction and integration among dynamic-static
hybrid simulation system. Users can not only acquire all the
varying production process data, but also observe the
relevant 3D animations to get intuitive impression about real
system operation. Therefore, the virtual factory can help
them make better decisions and promote competitiveness.
ACKNOWLEDGEMENTS
This work was supported by The National High Technology
R&D program of China (2009AA044701 & 2007AA40702).
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