18-10-2016, 10:54 AM
Implementation Of Distributed Control System In Process Control Management Using MATLAB
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Abstract: In recent years, process automation has being used in various industrial plants. Especially, Distributed Control
System (DCS) is more popular than any other control systems in the modern industrial processes. DCS is a computer control, a
software application and also designed to work on the computer for the process by providing with all the devices. The
advantages of the system are reducing process time, reducing labor costs, controlling, and monitoring real time condition. This
research aims to develop the “Real Time Graphical User Interface Monitoring and Network System” for Industrial Automation.
The current research project is based on the construction of DCS based bottle filling process system. The Industrial Local Area
Network (LAN) is built between the server for the operator and the clients for the two robots control and only one CNC milling
machine. In this research, the simulation of the overall process is conducted in real-time condition by using MATLAB software.
INTRODUCTION
A DCS is a system of controllers linked by a data network, as
a single system. Functionality, physical location, or both
separate these controllers. The DCS is used in complex
process applications where large amounts of I/O and data are
required, such as chemical plants or oil refineries. They are
well suited to batch processes and have an ability to handle
complex interlocks and timing between operations. DCS are
multitasking systems able to handle large common databases.
A DCS allows for various control loops, using graphical
representation of function blocks, and is easier to program
than ladder logic-based PLCs. Scan rates can be more
predictable than the PLCs. PLCs have scan rates dependent
on the amount of I/O [2]. A DCS has safety features,
redundancy, and even diagnostics built into its control
philosophy to be more robust with less down time [1]. This
project includes a computer connecting the devices setting in
distributed manufacturing plant. It uses parallel port pins
assigning input and output pins of the computer. The system
block diagram of distributed control system based
manufacturing process
DESCRIPTION OF THE DCS ELEMENTS
The DCS system consists of one or more of the following
elements.
• Local Control Unit (LCU). This is denoted as local computer
in Figure. This unit can handle 8 to 16 individual PID loops,
with 16 to 32 analog input lines, 8 to 16 analog output
signals and some a limited number of digital inputs and
outputs.
• Data Acquisition Unit. This unit may contain 2 to 16 times as
many analog input/output channels as the LCU. Digital
(discrete) and analog I/O can be handled. Typically, no
control functions are available.
• Batch Sequencing Unit. Typically, this unit contains a
number of external events, timing counters, arbitrary
function generators, and internal logic.
• Local Display. This device usually provides analog display
stations, analog trend recorder, and sometime video display
for readout.
• Bulk Memory Unit. This unit is used to store and recall
process data. Usually mass storage disks or magnetic tape
are used.
• General Purpose Computer. This unit is programmed by a
customer or third party to perform sophisticated functions
such as optimization, advance control, expert system, etc.
• Central Operator Display. This unit typically will contain one
or more consoles for operator communication with the
system, and multiple video color graphics display units.
Data Highway. A serial digital data transmission link
connecting all other components in the system may consist
of coaxial cable. Most commercial DCS allow for redundant
data highway to reduce the risk of data loss.
• Local area Network (LAN). Many manufacturers supply a
port device to allow connection to remote devices through a
standard local area network.
DISTRIBUTED CONTROL NETWORKS FOR BOTTLE
FILLING PROCESS
At first, the bottle is transferred to the machine through
conveyor continuously. The bottle is transferred through air
conveyor, then to Rinser. The bottles arrived to the rinser, the
machine start to rinse through the bottle nip clamping and
turning over 180 degree. The bottle turns over to origin after
rinsing. Then the machine starts to fill the water into the
bottles. And then start to cap onto the bottle mouth using filling
valves assemblies respectively. So capping is performing. The
bottle is transferred to the conveyor belt after capping. The
machine will start to the next working procedure after the
bottle is transferred to the conveyor belt. Filling valves
assemblies use counter pressure filling system. It is designed
for automatic and continuous operation. It can cope with
various types of bottles simply with changing the filler bowl
height and filling valves assemblies.
SIMULINK Model for PLC Remote Device
There are two main functional blocksets for PLC. They are
PID controller for stability analysis and the PLC remote
device. The rate limits is for applying the response limitation
for PLC plant after controlled with PID. The saturation blockset
is for supporting the rate limits input to control the process.
The PID controller is for process control stability
determination. The PLC is the main controller of the bottle
filling process and there are three stage control scan. They
are input scan, program scan, and the output scan. Before the
program scan, the input commands are analyzed by using the
situation of process. Therefore the time span of program scan
is longer than other two scans such as input and output scan.
But the debugging state of the PLC remote device button to
control the process of bottle filling system has been reached
and the simulation result for PLC remote device was
evaluated by using MATLAB SIMULINK model.