Virtual Factory Integrated Manufacturing System for

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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Virtual Factory Integrated Manufacturing System for