Industrial Communication Protocol

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Table of Contents

Introduction
Process Automation Protocol
Building automation protocols
Substation automation protocols
Automobile / Vehicle protocol buses
References

Introduction

Industrial communication applications have multiple communication peripherals precursor to connect industrial system with the outside world. This has been possible because of new microprocessors which are specially made for these kinds of applications. To give response to the users the suppliers are using the processors for improving the functions. They are changing their choices from proprietary communication protocols to open-standards protocols where networking technology from other industries is borrowed. This change is because of the requirements for greater communications between industrial devices and the world around them. The communication protocols like TCP/IP,Controller Area Network (CAN) and Universal Serial Bus (USB) are being used by them. These protocols are also proving themselves a great necessity for industrial design and are best suited to a specific use. The easiest communication interfaces for industrial equipment are serial interfaces like RS-232, RS-422 and RS-485, which are used by servos, controllers, actuators, simple sensors, valves and for communication (Graham Morphew, 2004).

Process Automation Protocol

Controller Area Network: This communications bus is used to control applications and proves to be highly reliable data. It has very good error detection. It was basically developed for using in the cars. Now it has multiple uses with other industrial automation and applications. It operates up to 1 Mega bits per second. Its sub bus is known as Local Interconnect Network (Controller Area Network (CANbus), 2006).

Now we will discuss how CAN works? Data messages which come from any node on CAN bus do not possess addresses for transmitting node and receiving node. In spite of this the content of the message is named by an identifier. These nodes apply an acceptance test on the identifier to check if the message is related to the particular node. The related message will be processed otherwise it will be ignored. The identifier also decides the main concern of the message. If there is a situation where two or more nodes try to transmit the messages, the message is sent on the priority basis. (Controller Area Network How CAN Works, 2006).

Lets discuss now the impelmentation of CAN. For all implementations of CAN communication is like two peas in a pod. Basic CAN and Full CAN are the two ways of implementation. Basic CAN: There is a link between the CAN controller and the associated microcontroller in Basic CAN configuration. The microcontroller deals with every message. Full CAN: They have additional hardware to provide message server that automatically transmits and receives messages without interfering microcontroller (Controller Area Network Implementations, 2006).

It is used in many network implementations, including CANopen and DeviceNet.

EtherNet/IP: During 1990s, Ethernet networks were used in manufacturing environments. It is a communication network planned for industrial environment and time critical applications. It provides robust physical layer options for industrial environments. It offers producer consumer services. It collects data from single network. It provides flexible installation options. It incorporates the TCP/IP suite. It uses the standards of Institute of Electricals and Electronic Engineers (IEEE). It is friendly with accepted communication standards. In Ethernet/IP and CIP the exchange of time critical data is based on producer-consumer messaging model where a transmitting device produces data on the network and it is consumed by the receiving devices (Network Infrastructure for EtherNet/IP; Introductions and Considerations, 2007).
Host Link: This protocol is an autonomous file transfer program that helps the users to move files easily and efficiently from PC client software. Users can transfer files with translation parameter templates. For this they use the unique features of flexible file types and whenever the transfer is done it reduces the need to reset complicated parameters (UNISYS A-Series File Transfer, 2006). Its benefits re given below (UNISYS A-Series File Transfer, 2006):
- it uses MCP security
- it has graphical user interface
- Clients are presentes for LAN, Windows and DOS gateway versions
- It encourages batch mode transfers
- There is no separate file transfer environmet required
- Windows and DOS clients share the same server programs related to host
- It has user definable file types
Mechatrolink: It is the main technology of the system. It agrees to the arrangement of multi-function and high performance system all at once as making tuning and maintenance of the system easier. It helps in performing a good range of tasks which makes work processes easier and it also saves time and money. An array of controllers and servo drives are the perfect choices for most machines in the market. It can be used for controlling high exactitude machines. It is supposed to be good for controls like synchronous motion. It makes users to control velocity in some complicated motions. It has following applications (Open Field bus Network Mechatrolink, YASKAWA):
- Cutting machines
- Plastic tape processors
- X-Z processing system
- Laser welders
- Printing machines
- Press brake
- Labelling machines
- Winding machines
- Chip mounters and handling robots
Optomux: This protocol is used by intelligent digital and analog I/O (Input/output) units. This unit is a 4-, 8-, or 16-point assembly that controls optically-isolated analog or digital I/O modules (Optomux). A removable brain is found in every Optomux I/O unit and every removable brain has a microprocessor,. That microprocessor helps in communication with the host computer and it also controls the plug-in I/O modules (Optomux).

Optomux I/O units have communication with the host computer which is a serial communication link over an RS-485. The serial data link is the work of two twisted pairs and a ground of 5 wires that becomes the medium of connection to Optomux I/O unit (Optomux).It is feasible to communicate up to 256 individual units and to contain a total of 4,096 digital and analog I/O for a single serial data link. The RS-485 serial data link has an outstanding noise resistance (Optomux).This can lessen the cost of wiring. It reduces the requirement of bringing large bundles of field. It brings it to a central control location. These units can be placed for actual control. (Optomux).

Profibus: The industrial networking solutions of PI are based on two technologies: Profibus and Profinet. Profibus was first expanded in 1989 and now it is its 20^th anniversary in 2009. It is the worlds most successful field bus which has the installation of approximately 30,000,000 nodes and global support (Share Our Vision for Automation). Profibus, which is the worlds most successful fieldbus, has got more than 28 million devices installed by the end of 2008. Approximately 4.8 million of these devices were used in the process industries. The fieldbus diminishes hard wiring in the automation of production lines that is why it uses a single-cable bus structure for minimizing design and installation costs. Profibus is used for improving asset management, lower life cycle costs, better quality and higher productivity. For achieving these tasks it controls diagnostics. Profibus is concerened with the applications-specific functionality like Functional Safety and Motion Control that are on the same fieldbus (Share Our Vision for Automation: The Worlds Most Popular Field bus).
PROFINET IO: It is an open EtherNet standard automation from the point of view of Profibus international. Profinet IO behaves same like profibus acts on Ethernet.It focuses on programmable Controllers at a maximum speed, whereas Profibus exercises cyclic communications. While doing so it maintains maximum speed of 12Meg baud. It exchanges data with Programmable Controllers in contrast; Profinet IO exchanges data with Programmable Controllers over Ethernet and for this it takes the help of cyclic data transfer. The data is restricted in pieces in both systems which has the total number of I/O points in a system module. Three different communication channels help Profinet IO in substituting data with programmable controllers and other devices. It is a unique industrial Ethernet application layer which puts forward many benefits over competing application layers as follows (Profinet Overview:
- PROFINET Unplugged An introduction to PROFINET IO):
  - High Speed orientation: High speed message exchange is possible by the real time communication channel through by passing the time required to process the TCP/IP
  - It supports for time critical motion control applications
  - It is used for Distributed Intelligence
  - It is Easy for installation
  - It has short startup
  - It takes minimum commissioning time and engineering support
  - Nearly identical Siemens S7 PLC are used for integration to Profibus
Modbus/TCP: Modicon developed Modbus originally and presently the Modbus IDA user organization manage it. This protocol is the type of an open master/Slave This task can be performed on different physical layers. It has got seventh place in OSI model. Modbus-TCP refers to the application of this protocol on the top of Ethernet TCP/IP. It is an open industrial Ethernet network about which the Modus-IDA User organization gives details that is in co-operation with the Internet Engineering Task Force (IETF) as an RFC Internet standard (Modbus-TCP Industrial Ethernet Protocol Overview, 2008). Modbus/TCP has not been new. It is in existence since 1979 and since then Modbus protocol version has not been changed. It has been adapted to TCP/IP as the data transmission protocol (Modbus-TCP Industrial Ethernet Protocol Overview, 2008).
Modbus Plus: Schneider and Modicon developed it originally and now it is managed by the Modbus-IDA user organization. This fieldbus network is used globally. Its main application area is in Europe and Schneider and Modicon maintains its automation systems. Variety of diferent products like Inverters, Drives, PLCs, and I/Os have good connection with Modbus Plus. Modbus Plus is a Field bus of Master/Slave type where RS-485 transmission technology is used and It is also a symbol of fleeting protocol for industrial control applications. This network allows devices to exchange messages from remote locations and it also can control and monitor the processes. Modbus Plus provides services like input/output subsystems which prove to be very competent. Modicon Modbus Plus Distributed I/O (DIO) Drop Adaptors and Terminal Block IO/TIO can have place on remote IO sites and from where they can perform the functions like controlling the field devices on the network link (Modbus Plus- Local Area Network, 2008).
Modbus-NET: This project is expanded for an open source ModBus communication component especially for.NET platform.The Visual Studio.NET 2008 and.NET Framework 3.5. will be the advanced instruments for this program. They will also work like a platform. VB.NET will be the advanced language for this program (ModBus.Net).

Building automation protocols

BACnet: An Official Website of ASHRAE SSPC 135 says about BACnet It is a Data Communication Protocol for Building Automation and Control Networks is developed under the sponsorship of the American Society of Heating, Refrigerating and Airconditioning Engineers (ASHRAE). It is a European standard and an American national standard in many countries. It is also an ISO global standard. ASHRAEStanding Standard Project Committee miantains and sustains this protocol. If BACnet performs in commercial products, it has some achievements (BACnet: Official Website of ASHRAE SSPC 135, 2009).

The official website of ASHRAE SSPC 135 investigates that from the past ten years BACnet has been communicating by using standard IP networks. The committee of ACHRAE has made a new working group to examine the opportunitie in the information technology industry just to make sure that BACnet absorbs well in corporate infrastructure and it can be expanded in to the emerging market areas facilitated by ubiquitous IP networking. BACnet is supposed to be a grown-up technology. Since 1995 it has always adapted to changing needs without loosing the steady foundation and has assured interoperability (BACnet: Official Website of ASHRAE SSPC 135, 2009).

LonTalk: The LonTalk Protocol that is predetermined in Neuron Chips is present in every LonWorks device. It makes all LonWorks devices communicate with one another using the protocol. For using this protocol on any processor; Echelon released a downloadable reference implementation on October 26th, 1999. ANSI approved standard EIA/CEA-709.1-A-1999 has descibed this protocol very well (The LonTalk Protocol).

This protocol was discovered by Echelon. It has many obvious modern functions and features. It was planned to facilitate extremely consistent and hierarchical networking among various control devices which are introduced by different suppliers.It was observed that Interoperability among devices demanded the implementation of the protocol in one and the same manner within all networked devices and also the need of the foundation of the reliable and consistent means of broadcasting, receiving messages and transmitting among Long Talk based devices was noticed. The implementation of protocol in Neuron Chip makes a foundation of interoparability in the devices (The LonTalk Protocol).

While publishing and incorporating the protocol into open standards like Control Network Protocol Specification, the Protocol Patent License Agreement had two purposes:1) the implementation of the protocol would be fully interoperable and could not be customized to make it non interoperable 2) the implementation would be achieved with Echelon protocol patents. It is must to apply the protocol fully to ensure interoperability between devices. Partial protocol implementations and deviations from the protocol specification put interoperability at risk. That is why they are strictly prohibited and on that basis the Agreement can also be terminated (The LonTalk Protocol).

Substation automation protocols

IEC 61850: It is launched just now with some international standards for communication in substations. It incorporates all protection, control, measurement and it also monitors functions within a substation. It also provides the means for high-speed substation protection applications. It joins the convenience of Ethernet with the performance and security which are the vital substations today (IEC 61850 Standard, 2008).
DNP3 Distributed Network Protocol: The expansion of DNP3 has been a widespread task. It manages the actions like standards-based Interoperability between substation computers, RTUs and master stations that is for the electric utility industry. The time frame is also considered to be the important function to meet current requirements. Distributed Network Protocol is now being used extensively in water that can be waste water, in transportation and in the oil and gas industries (A Forum for Supporters of the Distributed Network Protocol, 2009).

Automobile / Vehicle protocol buses

Local Interconnect Network(LIN): The LIN bus system supports serial communications protocol. This bus is a single master/ multiple slave that uses single wire for transmitting data. This system is based on a UART/SCI hardware interface that is common in many of microcontrollers. The components can be driven without crystal or ceramic resonators for minimizing costs. The correct transmission and reception of data is possible through time synchronization. This bus observes out of order nodes in the network. Data check and parity check make sure the safety and error detection (AN1278 Application Note: LIN (Local Internet Network Solutions, 2002).
Flex Ray: It is a newly developed serial bus system that transfers data quickly between vehicle components. It facilitates other systems to be networked accurately and safely. The electronic driver assistant system is becoming more complicated continuously. New chassis and drivetrain control systems demand very quick high data transfer to function successfully. Flex Ray has a major advantage that is its high data transfer rates which is up to 10 MBit per second; it is twenty times faster than the conventional CAN bus system. A second Flex Ray communication channel performs as a back-up, providing redundancy to provide with outstanding safety at all times. In case one channel does not function correctly, the other one is still available. For non safety-critical systems, a single channel can be used for transferring data speedily. These advantages produce drastically greater driving comfort and safety, allowing on-board systems to communicate more quickly and more safely (Flex Ray).
J1708: This SAE specification is mainly designed for heavy duty vehicles for example trucks and busses. This protocol supports serial communications between modules and microcontrollers. It benefits are (Introduction to SAE J1708):
- It minimizes the hardware cost
- It offers flexibility for further expansion
- It uses standard industry electronics

This protocol generally talks about the lower layers of OSI model. It supports the network of bus topology. It is efficient in detecting errors. It can also handle the conflict among messages during transmission (Introduction to SAE J1708).

References

A Forum for Supporters of the Distributed Network Protocol, 2009, published by DNP.

AN1278 Application Note, LIN (Local Interconnect Network) Solutions, 2002, published by Microcontroller Division ApplicationsN

Bacnet, 2009, sponsored by ASHRAEN

Controller Area Network (CANbus), 2006, sponsored by M.J. Shofield. Web.

Flex Ray, sponsored by BMW, 2009.

IEC 61850 Standard, 2008, AREVA.

Introduction to SAE J1708, published by KVASER. Web.

ModBus.Net, sponsored by Ohloh Root. Web.

Modbus Plus- Local Area Network, Interbus fieldbus network technology overview, 2008. Web,

Morphew, Graham, Choose carefully your industrial-strength comms protocol, 2004, published by EE Times. Web.

Open Field bus Network Mechatrolink, published by YASKAWA. Web.

Optomux. Web.

Profinet IO Overview, PROFINET Unplugged An introduction to PROFINET IO, 2009. Web.

Share Our Vision for Automation, sponsored by profibus- profinet. Web.

The LonTalk Protocol, published by Echelon. Web.

UNISYS A-Series File Transfer, published by Virtual Soft. Web.

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