A Review on ZigBee based Industrial Automation using PLC


A Review on ZigBee based Industrial Automation using PLC





AbstractIn today’s modern world the industrial sector has
shifted from the classical methods of Control and Automation to the state of
the art techniques like wireless Networks. These encouraged to industries to
attain a higher growth and production, with greater Quality as well as quantity
which consequently gave rise to reduction in costs of the products. This type
of automation is gaining popularity at a very slow pace due to huge initial
costs associated with it. This problem can be resolved by promoting ZigBee
based wireless Networks interfaced to Programmable Logic Controllers for state
of art control in industrial automation, which might encourage the industries
to take the path of modern Wireless Cost effective automation. This paper focuses
on the most widely used wireless standard in Wireless Sensor Networks, a ZigBee
technology and its role in Industrial Factory Automation. So there is a great
potential of Wireless Sensor Network in industrial, consumer and commercial
application. Also this paper shows efforts of role of ZigBee in various
industrial applications.
KeywordsIndustrial
Automation, Programmable Logic Controller, ZigBee based wireless Networks,
ZIGBEE based Automation System.
I.     
Introduction
Industrial
Automation technologies with wireless Network such as Industrial Distributed
Control System (DCS), Factory automation and industry automation technologies
are rapidly changing due the recent development of Solid State Electronics. One
of the most promising protocols for wireless networking and Factory automation
is ZigBee based automation. The ZigBee has advantage of low power consumption,
low cost, and support for various cluster automation network configurations. IEEE
802.15.4 protocol, which describes MAC and Physical layer of the ZigBee [2]
protocol stack, isthought up to be used in special purpose systems, since they
require low consumptions and do not necessitate an high transmission speed.ZigBee
is one of the new technologies enabling Wireless Personal Area Networks (WPAN).
ZigBee gives a specification for a suite of high level communication protocols using
small, low-power digital radios based on the IEEE 802.15.4 standard [3].

 Fig.1.Tarang ZigBee

 


The
technology is simpler and cheaper than other WPANs such as Bluetooth technology.
ZigBee protocols are provided for use in various embedded applications
requiring low data rates and low power consumption. Though WPAN covers only a
few meters, 30 feet in thecase of ZigBee; the network will have several layers,
so designed as to enable intrapersonal communication within the network,
connection to a network of higher level and ultimately an uplink to the Web [4].
PLC’s
are solid state devices used to control process or machines.  They 
can  store instructions  like 
sequencing  counting,  timing, arithmetic,  data 
manipulation  and  communication [7]. A PLC is an example of a
hard real time system since output results must be produced in response to
input conditions within a bounded time, otherwise unintended operation will
result.PLC reads the status of the external input devices, e.g. Keypad, sensor,
switch  and  pulses, 
and  execute  by  the
microprocessor  logic,  sequential, 
timing,  counting and arithmetic
operations according the status of the input 
signals  as  well 
as  the  pre-written 
program stored in  the PLC [8].
The generated outputs are sent to 
output  devices  as 
the  switch  of 
a  relay electromagnetic  valve, 
motor  drive,  control 
of a machine or operation of a procedure for the purpose of machine
automation or processing procedure.
The
paper is organized as follows. Section II gives automation type. Section III
gives programmable logic controller. Section IV presents ZigBee architecture.
In section IV industrial applications review is presented. The conclusions
presented in section V.  

II.   Automation

Automation is the process of tocontrol systems (such as numerical
control, programmable logic control, and other industrial control systems), in
concert with other applications of information
technology (such as computer-aided
technologies (CAD, CAM), to control industrial machinery and processes,
reducing the need for human intervention. In the scope of industrialization,
automation is a step beyond mechanization. Whereas mechanization provided human
operators with machinery to assist them with the physical requirements of work,
automation greatly reduces the need for human sensory and mental requirements
as well. Processes and systems can also be automated.
Specialized
hardened computers, referred to as programmable logic controllers (PLCs), are
frequently used to synchronize the flow of inputs from (physical) sensors and
events with the flow of outputs to actuators and events. This leads to
precisely controlled actions that permit a tight control of almost any
industrial process. There exist two types of automation wired and wireless
automation [5].
·        
Wired Automation
·        
Wireless Automation
The
demand for wireless technology in home automation systems has recently been
increasing due to several advantages such as installation cost reduction, easy
placement, easy extension, aesthetic benefits, and mobile device connectivity.
Among the many wireless technologies available, ZigBee is one of the most
useful for home automation. A wireless home networking system can be configured
using ZigBee alone [7].
Wireless
technology spans a distance beyond the capabilities of typical wiring. It can
provide a backup communications link in case of normal network failure, link
portable or temporary workstations, wireless technology can overcome situations
where normal cabling is difficult or financially impractical. In wireless
technology fault finding is easy as compared to wired technology.

III. Programmable
logic controller (PLC)

A
PLC is a programmable logic controller which is known as digital computer used
to automate industrial processes, such as control of machinery on factory assembly
lines. Unlike the general purpose computers, the PLCis designed for multiple
input and multiple output arrangements, extended temperature ranges, immunity
to electrical noise, and resistance to vibration and impact. PLCs have been
gaining popularity on the factory floor and will probably remain predominant
for some time to come. Most ofthis is because of the advance they offer: cost
effective,flexible, reliable, etc.[6]

Fig.2. PLC Block Diagram
Fig.
2 shows block diagram of PLC. A small PLC has a fixed number of connections
built in for inputs and outputs. Expansion are available if the base model does
not have sufficient I/O. Programs to control machine operation are typically
stored in battery-backed RAM or other non-volatile flash memory. These PLC
programs are typically written in a special application on a personal computer,
andthen downloaded to the PLC over a cable. The PLC can bereprogrammed several
times, thus making it adaptable to the process changes required by the
company/organization [13].

·        
ZigBee & PLC Controlled Batch
Process

ZigBee
acts as transceiver. A pair of ZigBee transmitter and receiver is used where
wireless exchange of data takes place and hence two way communication is done.
The application “Monitoring” takes place at the field/process site. It is
placed in a remote area and consists of sensors and actuators [1].
The
process controlled in the project using a PLC is a Batch process used to
manufacture a chemical and the parameters to be controlled and measured is
level.
Benefits
of Batch Process
·     A batch
process can be used to automate much of the work.
·     Batch
processing can save time and energy by automating repetitive tasks.
·     Batch
time can be adjusted to meet quality specs
·     Slow
dynamics permit real-time calculations
The
BATCH PROCESS setup is placed in a remote area (field/process site) and is
controlled from the control room wirelessly using TARANG ZigBee where PLC,
SCADA and the control panel are placed. The process is controlled through
SCADA&PLC in auto mode and can also be controlled in manual mode. The
process can be controlled and monitored directly from SCADA and also from the
control panel [1].
       The main components are TARANG ZigBee and
PLC which control the whole process. The TARANG is used as the source and which
is used in direct mode. PLC is used to control and monitor the batch process [1].

IV. Zigbee
architecture

The
ZigBee Standard has evolved standardized sets of solutions, called ‘layers’.[4]
These layers facilitate the features that make ZigBee very attractive: low
cost, easy implementation, reliable data transfer, short-range operations, very
low power consumption and adequate security features. Fig. 3 shows layered
architecture.
Network
layer
:
Network
layer interfaces between application layer and MAC Layer. This Layer is
responsible for network formation and routing. Routing is the process of
selection of path to relay the messages to the destination node. This forms the
network involving joining and leaving of nodes, maintaining routing tables
(coordinator/router), actual routing and address allocation. ZigBee coordinator
or router will perform the route discovery. This layer Provides network wide
security and allows low power devices to maximize their battery life. From the
basic topologies, there are three network topologies are considered in
IEEE802.15.4 are star, tree Network and mesh [8].
Application
Support layer:
The
application Layer is the highest protocol layer and it hosts the application
objects. ZigBee specification separates the APL layer into three different
sub-layers: the Application Support Sublayer, the ZigBee Device Objects, and
Application Framework having manufacturer defined Application Objects.
·      The application objects (APO):This part of layer controls and manages the protocol layers in ZigBee device. It is a
part of software which controls the hardware. Each application objects assigned
unique end point number that other APO’s can use an extension to the network
device address to interact with it.
·      ZigBee Device Object:The key
definition of ZigBee is the ZigBee device object, which addresses three main
operations; service discovery, security and binding. The role of discovery is
to find nodes and ask about MAC address of coordinator/router by using unicast
messages.
·      Application support sub layer:The
Application Support (APS) sub layer provides an interface between the NWK and
the APL layers through a general set of services provided by APS data and
management entities.
·      Security service provider:ZigBee provides security mechanism for network layer and
application support layers, each of which is responsible for securing their
frames [8].
Physical
layer
:The
physical layer of the IEEE802.15.4 standard is the closest layer to the
hardware, which control and communicate with the radio transceiver directly. It
handles all tasks involving the access to the ZigBee hardware, including
initialization of the hardware, channel selection, link quality estimation,
energy detection measurement and clear channel assessment to assist the channel
selection. The IEEE 802.15.4 physical layer accommodates high levels of
integration by using direct sequence to permit simplicity in the analog
circuitry and enable cheaper implementations[7].Supports three frequency bands,
2.45GHz band which using16 channels,915MHz band which using 10 channels and
868MHz band using 1 channel. All three using Direct Spread Spectrum Sequencing
(DSSS) access mode [8].
Media access
control layer
:
This
layer provides interface between physical layer and network layer. The MAC data
service enables the transmission and reception of MAC protocol Data Units
(MPDUs) across the PHYdata service.This provides two services; MAC data
services and MAC management service interfacing to the MAC sub Layer Management
Entity (MLME) Service Access Point called (MLME-SAP). MAC layer is responsible
for generating beacons and synchronizing devices to thebeacon signal in a
beacon enabled services [8].

Fig.3. 802.15.4 ZigBee Stack Architecture
ZigBeeis
the wireless technology falls in the category of wireless domain like GSM and
RF technology. It indicates that ZigBee reduces the cost and maintenance of the
wires used for connections. Thus ZigBee replaces the wired technology and
provides a wireless communication [1].
As
the wireless PLCs use modem for transmitting signals from PLC to the process
here we are using ZigBee as the communication interface which is used for
transmitting and receiving the signals from the PLC to process and vice-versa.ZigBee
is a wireless network developed as an open global standard to address the
unique needs of low-cost and low-power wireless personal area networks (WPANs).
This wireless network uses full advantage of 802.15.4.

V.    Industrial Application Review

Following
are some of the Industrial applications discussed.
·        
Industrial Automation by ZigBee
Based Wireless Remote Controller:
In
this application an integrated remote controller is used to control electric
appliances in the home with no extra attachment of communication device to the appliances,
using ZigBee protocol and infrared remote controller technology. It is cost
effective technology for any home appliance by using ZigBee protocol as a wireless
communication technology[12].
·        
Real Time ZigBee Based Network
for Home Automation Environment.
In
this application it is shown that a two-tiered architecture designed to connect
nodes that exchange messages with Real-Time constraints within a Home and
Building Automation. The architecture model here proposed solves the problems
of limited transmission range of the IEEE 802.15.4/ZigBee protocol, allows to
control and monitor the various devices in a centralized approach both locally
and remotely (using the Internet access) [11].
·        
Water Level Control System Using
PLC andWireless Sensors
In
this application describes designed and implemented a water level control
system based on the usage of PLC system and wireless sensors. One of the main
advantages of using a design based on PLC is the simplicity, flexibility and
reliability in comparison with other classic control solutions. The study tests
were performed by using an experimental SIEMENS LOGO! 24RL PLC system. In this
paper are presented two water level measurement systems, one uses resistive
electronic sensors, contactors and a contactor coil that turns off the water
pumping installation, and the other one uses wireless sensors and a PLC. The
main disadvantage of contactor is the reduced capacity of resisting to
overloads and short-circuits; this disadvantage can be eliminated by using
ultra fuses. The system based on PLC and wireless sensors is cost effective and
allows easy customization. Nowadays PLC and wireless sensors based systems
represent modern solutions that are suitable for controlling the time driven
event systems such as the case of water tank control [9].
·        
Wireless Machine Monitoring And
Control For Educational Purpose
This
application gives knowledge of educational pneumatic machine with replacement
of Programmable Logic Controller that being used before to control part or pneumatic
and electro pneumatic components using Data Acquisition Card (DAQ) and ZigBee
network for wireless communication. SCADA measurement is done with NI LabVIEW
as software with analysis and a customized user interface. The complete
automation process did show that machine monitoring and control using LabVIEW
and DAQ is reliable and easy to use software forGUI applications [10].

VI.
Conclusion

The
review on a ZigBee and its applications in industrial automation system is
presented. Paper focuses on traditional automation methods and advanced
wireless networks so as to might encourage the industries to take the path of
modern Wireless Cost effective automation so there is a great potential of
Wireless Sensor Network in industrial, and many other commercial applications.
ACKNOWLDGEMENT
The
authors would like to thank reviewers of this paper for their valuable comments
and also to the sponsored company.
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