Connect to the Benefits of Digital Industrial Networks

More users, system integrators, and manufacturers of control hardware and software are realizing the benefits of digital networks at the sensor, device, and fieldbus levels.In this kickoff of the "Year of the Network" series, Control Engineering asked leaders associated with 12 major industrial networks to reveal growth projections, ideal applications, views on standards, and future out...

By Mark T. Hoske, Control Engineering January 1, 1998


Networks and communication


Device-level networks

Sensor/actuator-level networks

Local-area networks

Sidebars: FutureNet: What’s Ahead From the field: Smar International Embracing an Ethernet-based Solution on the Factory Floor

More users, system integrators, and manufacturers of control hardware and software are realizing the benefits of digital networks at the sensor, device, and fieldbus levels.

In this kickoff of the “Year of the Network” series, Control Engineering asked leaders associated with 12 major industrial networks to reveal growth projections, ideal applications, views on standards, and future outlook and provide an network overview. A supplier of hardware and software for more than 50 networks also looks at what’s ahead.

Far from consolidation or fallout among industrial networks, all 12 predict significant growth from 1997 to 2000, with more than one network likely per site. It seems likely that preferences by region and industry may also support multiple industrial networks.

Ethernet protocol, rapidly being accepted for use on the plant floor, instead of just above it, is also covered, along with several Ethernet industrial applications.

Unabridged text with many more details, may be found at Control Engineering Online, .

In an adjacent article, a system integrator describes types of networks and provides practical tips for selecting an industrial network for a particular application. An original equipment manufacturer (OEM) discusses cost savings and digital benefits.

Jump in and join users, integrators, and OEMs realizing the full benefits of digital information flow with industrial networks in this “Year of the Network.”


Levels: Sensor, Device, Field

Respondent: Barry Haaser, marketing director, Echelon Corp. (Palo Alto, Calif.) for the LonMark Association.

Echelon developed the LonWorks control network platform by assuming that application requirements are fundamentally the same in every industry. Today, more than 35% of Echelon’s customers (approximately 1,200) serve the process, discrete, and hybrid industrial applications.

LonWorks serves as a sensor network, device network, and field network. Since 1991, Motorola and Toshiba have shipped more than 4 million Neuron chips. In ’97, U.S. industry installed about 500,000 LonWorks-based nodes. LonMark Interoperability Association has 200 members.

Overview: A LonWorks network comprises intelligent devices (actuators, sensors, operator interfaces, controllers) that communicate using a common, seven-layered protocol over one or more media. Code is available, allowing LonWorks to port to other silicon solutions. Recent enhancements include faster Neuron chips and the LonWorks Networks Services (LNS) architecture, supporting interoperable tools, Microsoft Windows 95 and Windows NT-based human-machine interfaces (HMIs), component software with ActiveX objects, local and remote network access, and seamless Internet connectivity.


Level: Sensor

Respondent: Rich Canfield, director, Seriplex Technology Organization Inc. (STO, Raleigh, N.C.).

As a sensor/actuator network that sits at the lower end of the network hierarchy in cost and complexity, the Seriplex bus is seeing the primary driving market factors as cost driven.

At year-end 1997, there was an installed base of over 1 million Seriplex I/O points. STO expects to see Seriplex-based 1997 sales double in 1998, and double again by year 2000. Roughly 60 manufacturers provide Seriplex-compliant products. Particularly suited are applications that demand long distances between I/O points (little clustering) and flexible topology. The market looks bright for networks with a niche, adding value for the user. Standardized interfaces will make networks more transparent.

Overview: Seriplex Control Bus is a simple method of connecting control system input and output devices using a single cable. Introduced in 1990 after years of development and refinement, Seriplex Control Bus today has over one million I/0 points installed in over 2,000 installations. Users include automotive manufacturing and assembly, entertainment, semiconductor fabrication, material handling, and paper processing industries. Manufacturers, end-users, and institutions are members of Seriplex Technology Organization.


Levels: Sensor, Device

Respondent: Tom Lauterback, managing director, SERCOS N.A. (Elgin, Ill.).

Field networks seem to be the primary drivers of the market for digital networks; we do not consider SERCOS (SErial Real-time COmmunications System) to be a true fieldbus, though it performs many of the functions. We work with most if not all the networks, but do not have reliable numbers for nodes and sites.

More than 100,000 axes [of motion control] are installed. There are 11 members of SERCOS North America, dozens more in Europe (Interests Group SERCOS), and at least 10 in SERCOS Japan. SERCOS is strong in packaging, printing/converting, and auto manufacturing. Standardization give users portability and predictable results.

Overview: SERCOS is an open controller-to-intelligent digital drive interface specification (IEC 61491) designed for high-speed serial communication of standardized closed-loop data in real time over a noise immune, fiber-optic cable. SERCOS was created in 1986 by a consortium of manufacturers seeking an open (nonproprietary) communications system for intelligent drive technology. IEC and American National Standards Institute (New York) have the specification.

AS-Interface (AS-i)

Levels: Sensor

Respondent: Michael Bryant, executive director, AS-Interface Association (Scottsdale, Ariz.).

AS-Interface (AS-i) was conceived in 1990 as a cost-effective alternative to conventional hard wiring by a consortium of 11 European companies. AS-i provides high data integrity and versatile networking using a two-wire system to carry power and data. AS-i complements higher level fieldbuses. Since 1991, the AS-Interface Association, an independent nonprofit with more than 160 vendor companies, manages AS-i technology. Products number over 400. AS-International Association has 165 members; AS-Interface USA has 25.

AS-i has 600,000 nodes at 40,000 sites. AS-i users can expect better gateways to higher-level technologies, lower chip prices, and new AS-i master and slave chips.

Overview: Actuator Sensor Interface was introduced to the European market in 1993 and the U.S. market in 1996 as a new interface for industrial communication at the lower-most level. AS-i connects first and binary sensors and actuators with the primary control level, e.g. PLCs or PCs, via a bus line. A novel, simple connection technique allows easy linkage of the components. Untwisted and unshielded two-wire cable is used for transmitting data and energy within the network.

Overview source: AS-i: The Actuator-Sensor-Interface for Automation, Werner R. Kriesel and Otto W. Madelung, eds.


Levels: Sensor, Device

Respondent: Mark Knebusch, director of Interbus, Phoenix Contact (Harrisburg, Pa.).

The desire for reduced overall costs, especially for commissioning and troubleshooting, is what’s driving the overall market for industrial networks. At year-end 1997, Interbus expected more than 125,000 applications, and 1.7 million networked devices. The Interbus Club has more than 700 manufacturers; International Interbus Club has more than 400 members.

Applications particularly suited to Interbus include automotive, printing, material handling, and machine tools. Expect more application-specific products. De facto standards, networks with large numbers of vendors, give users freedom to choose what they connect to the network and more network-support choices.

Overview: Interbus is a device-level fieldbus designed by Phoenix Contact and released in 1987. It was opened to partners in 1990. It is fast, deterministic (token passing, ring topology), and has a strong following by drive manufacturers. Up to 512 “remote” nodes can be connected, each up to 400 m apart. Interbus also allows for secondary, 10 m loops; there can be up to 192 nodes in these “local” buses. Remote and local nodes use the same silicon chips but nodes are not interchangeable.

Overview sources: Understanding Device-Level Buses, by Bob Svacina, Turck Inc.; Phoenix Contact.


Levels: Device, Field

Respondent: Dave Lane, director of operations, Profibus Trade Organization (Scottsdale, Ariz.).

The market is driven by end-user desire for Profibus networks and related products. There are more than 1,100 Profibus products available for discrete and process automation.

Profibus has 1,350,000 nodes at 120,000 sites (15% U.S.). The organization has 620 members. Applications include factory automation and manufacturing with Profibus-DP and Profibus-FMS); building automation with Profibus-DP; and process automation and batch with Profibus-DP/Profibus-PA. Users can expect higher speed systems for discrete manufacturing, lower chip prices, new Profibus-DP and Profibus-PA products, and new Profibus Masters for Profibus-PA.

Users will search for faster, cheaper, smaller, and easier-to-install products. The market will be reduced to dominant product manufacturers; I believe Profibus, DeviceNet, ControlNet, and AS-Interface will dominate.

Overview: Profibus was by a German Ministry of Research & Technology request to develop a specification for fieldbus communications. A consortium completed development in 1989. Profibus-FMS (Fieldbus Message Specification) is a general-purpose solution for peer-to-peer communication tasks. Profibus-DP is for high-speed data communication in factory automation. Profibus-PA is for process automation. Profibus complies with EN 50 170. There are more than 1,130 products from 270 manufacturers and 17 Profibus User Organizations.


Level: Sensor, Device

Respondent: Bill Moss, executive director, Open DeviceNet Vendor Association (ODVA, Coral Springs, Fla.).

End-users want to take advantage of all benefits that device-level networks provide, such as reduced hard wiring and increased diagnostics. DeviceNet had 160,000+ verified nodes installed by year-end 1997. By year 2000, DeviceNet nodes may exceed 3 million. All 218 ODVA members are industrial; only manufacturers are members. There are 1,498 registered DeviceNet specification holders in the industrial market. System Integrator/OEM User Groups of ODVA have 98 participants.

Industries include automotive, semiconductor fabrication (chip-manufacturing), electronics manufacturing, food and beverage, batch, chemical processing, assembly, packaging, and material handling. It is based on commercially available CAN chips from 15 suppliers, costing as low as $2 each.

Standards are becoming irrelevant. ODVA, a de facto standards organization with an agile revision process, provides conformance test software, and conformance labs in Germany, Japan, and U.S.

Overview: DeviceNet is a low-cost communications link to connect industrial devices (limit switches, photoelectric sensors, valve manifolds, motor starters, process sensors) to a network. Performance and cost are backed by technical support, development tools, configuration software, and interoperable products. It operates on two twisted pairs of wire plus drain (to provide a low-resistance ground return at any point along the shield) in one cable. Two wires provide 24 V dc power and signal, unlike other networks that only supply the signal. End-users can configure online and add a device or machine to a production line without powering down. Producer/ consumer technology allows devices to exchange data on an event or cyclical basis. DeviceNet provides peer-to-peer and master/slave communication.

Smart Distributed System

Levels: Sensor, Device

Respondent: Bill Arnold, senior marketing specialist, Business Development, Honeywell’s Micro Switch Div. (Freeport, Ill.).

Industry is becoming attuned to the benefits possible from using industrial device-level networks. Incentives include flexibility and reduction in costs, increased productivity, predictive diagnostics; best-in-class components and options for controller architecture, and lower upgrade and life-cycle costs.

Smart Distributed System nodes have grown to more than 200,000 at year-end 1997. By year-end 2000, nodes are expected to surpass 1.5 million. Markets include package distribution, electronic assembly, packaging equipment, and automotive factory floor. Over 100 vendors are developing products. “Smart Society” is the user group.

Overview: Smart Distributed System, introduced by Honeywell’s Micro Switch Division in 1994, includes a device-level control network that is CAN-based (Control Area Network) for speed and reliability. Application Layer Protocol provides a device-level control-oriented network, which can be scan or event-driven, master-slave or peer-to-peer. It supports devices such as sensors, actuators, analog I/O devices, transducers/transmitters, motion control, PCs, PLCs, and distributed-control devices. This open standard has published specifications, no royalties or fees, widely available silicon, and participation by a large and growing number of industrial control suppliers. Underwriters Laboratories administers a verification testing program. Transmission speeds decrease with length. A repeater increases distance. Maximum network nodes is 64.


Level: Field

Respondent: Bill Moss, executive director, ControlNet International (CI, Coral Springs, Fla.).

Many applications for industrial field networks require tight coupling between the controller and I/O devices, along with determinism and repeatability. No existing network on the device or information levels could accomplish this effectively, until ControlNet.

In under a year, manufacturers have installed more than 20,000 ControlNet nodes, in hundreds of applications. By year 2000, more than 500,000 nodes are expected. All 38 CI members are from industry—35 manufacturers, 3 end-users. Applications include automotive, chemical, power generation, and forest products, especially controller-to-DCS communications, drive synchronization, and linking of multiple controllers to multiple HMI devices.

Customers will demand that networks integrate, as do DeviceNet, Ethernet, and ControlNet. CI members direct future enhancements; Special Interest Groups will look at increasing data rates and expanding the number of object definitions to include more types of devices.

Overview: ControlNet network is a 5 Mbit/sec communications protocol that provides time-critical control and a high-speed link between controller and devices. It allows users to accurately predict data transmission and guarantee its arrival at the same time every time—deterministic and repeatable performance. It is an open network based on the latest communication technology available—producer/consumer. As a “masterless” network, multiple redundant controllers can reside on it.


Levels: Field

Respondent: John W. Beeston, director international communications, WorldFIP (Kilsby, Rugby, U.K.).

There is no industrial, device or field network market, only markets for industrial equipment, devices (sensors and actuators are distinct markets) and equipment (such as motor control centers, variable-speed drives, controllers etc.) Users buy equipment from their preferred supplier and take the bus provided.

WorldFIP sites and nodes at the end of 1997 were 5,000 and 350,000, respectively. At the end of year 2000, 7,000 sites and 500,000 nodes are expected. Sites often have several networks.

There are 50 WorldFIP industrial equipment manufacturers and 100 WorldFIP members. Applications include machine control, steel, and automotive assembly, as a high-speed process-control backbone, and in transportation, utilities, and building services.

Overview: WorldFIP is a full-function producer/consumer-style fieldbus started in 1987 (as FIP) by EXERA, a group of multi-industry users. Now a European Standard, it is supported by the international WorldFIP nonprofit association. Major vendor promoters include Cegelec and Groupe Schneider. Network access is controlled by a centralized bus arbitrator (optionally multiple redundant), which guarantees determinism of cyclic time-critical traffic and allocates spare time to events and messages. It uses the producer/consumer model and is deterministic.


Level: Field

Respondent: George Beason, executive director, ARCNet Trade Association (Boerne, Tex.).

Low-cost, robust, deterministic qualities of ARCNet fieldbus technology drive the market up. Users seek low-cost, low-maintenance solutions when retrofitting or creating new systems. About 4.5 million ARCNet nodes are in industry; 6 million nodes will be installed by year-end 2000. There are an estimated 300 equipment manufacturers. ARCNet is often embedded into machinery. About 50 members are in the ARCNet Trade Association and the ARCNet User Group (Germany). ARCNet is used primarily in building automation, SCADA systems, motion control, security, printing, and automotive.

ARCNet technology is emerging with higher speed chips of up to 10 Mbit/sec, much smaller chip packages, and higher performance 16-bit interface capabilities. ARCNet’s basic ANSI 878.1 standard gives end-user a level of confidence for interoperability between competing manufacturers and suppliers.

Overview: ARCNet (Attached Resource Computer Network) is a controller-level fieldbus network that provides the physical and data-link layers of the International Standards Organization OSI (Open Systems Interconnect) Reference Model. ARCNet provides for the successful transmission and reception of data packets between two network nodes. A node is an ARCNet controller chip and cable transceiver connected to the network. ARCNet’s performance is based on its deterministic, token-passing protocol, eliminating transmission collisions. A token is a unique signaling sequence passed in an orderly fashion among all active nodes. ARCNet Trade Association is an ANSI Standards development body for ARCNet product standards.


Level: Field

Respondent: John Pittman, executive director, Fieldbus Foundation (Austin, Tex.).

The market is driven by end-users’ desire to move away from older, centralized plant control strategies to distributed control in the field. Increasingly, users with mission-critical applications are choosing FOUNDATION fieldbus.

As of late 1997, there are approximately 30 FOUNDATION fieldbus systems in more than 25 countries. An estimated 1,200 to 1,400 devices based on FOUNDATION fieldbus specification have been installed. By year 2,000, approximately 80% of all new control systems with bus technology will be FOUNDATION fieldbus compliant.

Out of 120 members, 100 are suppliers and 20 are end-users; the 135+ member Control System Integrators Association (CSIA) also is a member.

The measurement and control community continues to demand a single international fieldbus standard. Recent balloting has demonstrated that a majority of IEC members support the FOUNDATION fieldbus specifications, included in the international standard. Fieldbus Foundation started interoperability testing of suppliers’ devices in 1997.

Overview: FOUNDATION fieldbus is an all-digital, serial, two-way communications system which interconnects fieldbus equipment such as sensors, actuators and controllers. As the base-level digital network in the hierarchy of plant networks, it serves as a Local Area Network for process and manufacturing automation instruments with a built-in capability to distribute the control application across the network. It is based on the ISO/OSI seven-layer communications model. FOUNDATION fieldbus retains the desirable features of the 4-20 mA analog system such as a standardized physical interface to the wire, bus-powered devices on a single wire pair, and intrinsic safety options. It enables increased capabilities from full digital communications; and reduced wiring and wire terminations due to multiple devices on one wire.

Mike Drakulich, Control Engineering , also helped with the article.

FutureNet: What’s Ahead

While reduced wiring installation costs are driving the device and field networks initially, in the longer term, users should see lower life-cycle and maintenance costs and higher reliability from improved diagnostics.

Users will see more intelligence distributed among the devices on the network vs. the traditional “master/slave” architecture. Open networks give users improved diagnostics and the ability to select best-of-class devices from multiple vendors. Also, open standards seem to be forming into “interoperable families” like DeviceNet/ControlNet and Profibus-DP/ PA/AS Interface that extend functionality from the device throughout the plant levels.

SST, formerly S-S Tech-nologies, (Waterloo, Ontario, Canada) designs and markets industrial communication products for 50 proprietary, custom, and open networks.

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From the field: Smar International

Smar International (Houston, Tex.) took the original Fieldbus Foundation specification and ran with it, making equipment and selling products over the past three years. While many installations weren’t the final Fieldbus Foundation specification, Smar has offered to upgrade the chip, upon request. Smar has more than 75 fieldbus installations.

Operators at a Mazatlan, Sin. Mexico, power plant, were afraid of a PC-based system at first, says Rogelio Berber Guzman, Instrumentation Department chief, C.F.E. CT Jose Aceves Pozos electric generating station.

“In the beginning, operators’ attitude was fearful since they were not familiar with PCs for process control, but it was also a challenge for them to operate the boiler from a PC screen instead of the two meters of panel used before. Nevertheless, today, operators handle the boiler easier, and they are satisfied since the response speed allows them more margin maneuverability than before.

“Our productivity is measured in function of time working. The fieldbus system has eight months running time without any fault,” concludes Mr. Berber Guzman.

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Embracing an Ethernet-based Solution on the Factory Floor

Long established in commercial circles as the most widely used local area network, Ethernet’s attractiveness stems from its inexpensive, readily available hardware and extremely fast response times.

PCs have moved beyond human-machine interface and supervisory control and data acquisition applications into the realm of real-time control. Available technologies include Microsoft Windows NT and high-performance Ethernet-based industrial I/O devices. These developments are making a serious impact on the manufacturing world, at a very reasonable cost.

PLC Direct by Koyo (Cumming, Ga.) responded to PC-based control’s need for reliable, low-cost, deterministic connectivity to PLC I/O devices with its new H2-EBC Ethernet Base Controller Module ( CE , Oct. ’97, pp. 86, 88).

Designed to work with PLC Direct ‘s I/O system, Think & Do Software (Ann Arbor, Mich.) offers PC-based control system software, including an HMI package. Enhanced with real-time functionality, the PLC Direct /Think & Do Ethernet solution steps beyond standard Ethernet, serving time-critical applications with deterministic capability. This is accomplished by controlling network traffic in a subset of the Ethernet standard. The system polls I/O bases one at a time, avoiding data collisions.

A systems integrator/OEM, Automation Engineering Inc., (AEI, Woburn, Mass.), provides machines and control systems for advanced motion control, vision inspection, and assembly operations within a variety of industries. AEI liked the ease of maintenance and low component cost advantage of the modules.

STP (Sherbrooke, Quebec, Canada), provides roto-molding equipment used to manufacture large molded parts such as canoes. Andre Glaude, electrical engineer, says STP chose Ethernet for its new-generation machines because it is “a standard network utilized in all industries. Customers feel secure with a known technology.” Mr. Glaude continues, “Our customers saved lots of programming time since they can transfer machine data directly into a widely used software package they understand, such as Excel.”

Ethernet overview: Ethernet is a registered trademark of the Xerox Corp. (Stamford, Conn.), although Digital Equipment Corp. (Shrewsbury, Mass.) and Intel Corp. (Hillsboro, Ore.) contributed to the development of the current standard (IEEE 802.3). Xerox publishes the standards.

Ethernet is a shared media LAN (Local Area Network), and one of the most widely used LAN access methods. Ethernet connects up to 1,024 nodes and operates at a speed of 10 Mbit/sec.

Alongside the original 10 Mbit/sec (10Base-T) Ethernet standard is the Fast Ethernet Standard (100Base-T). It is part of the same IEEE 802.3 CSMACD protocol, yet configured to achieve 100 Mbps data delivery speeds. The Gigabit Ethernet Alliance aims to help an IEEE committee quicken delivery to 1,000 Mbit/sec (1 GB) speeds, while maintaining compatibility with 10 and 100 Mbit/sec standards.

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