Networked I/O Strategies Connect

Year of the Network

Year of the network

Machine control

Fieldbus

I/O systems

Programmable logic controllers

PC-based control

Sidebars: Profibus automation Why Ethernet? Network on a chip

Pressures on manufacturing engineers to cut costs, commission production lines faster, and increase machine uptime never end. With every improvement come management demands for more.

The technologies that helped in the past are now often in the way of more improvements, but help is on the way. Many new technologies will solve these new problems. [See also an adjacent Year of the Network article for more applications of industrial network technologies.]

Collapsing architectures

The graphic from Rockwell Automation (Mayfield Heights, O.) shows a view of these changes. Sensors and actuators have been distinct components from signal conditioners. Wiring terminals were separate from input/output modules. The controller contains the entire system program.

Smart field devices now include signal conditioning and networking ability. Communicating directly to the controller, they eliminate much wiring. Intelligence and networking ability have been added to terminal blocks reducing wiring complexity and enclosure size. This technology has opened markets to many who offer products for any network.

The other collapsing architecture is the development of small packaged control products and intelligent I/O devices. The large controller and its often large program can now be replaced with control distributed around a production line.

“新控制系统必须灵活,聪明,faster, and cost-effective,” says Graham Harris, I/O systems business manager at Rockwell Automation’s Allen-Bradley. “A solution is the use of intelligent I/O systems to integrate the functions of stand-alone ‘black box’ products, such as programmable limit switches, weigh scales, flowmeters, motion controllers, and temperature controllers. By integrating these functions into an intelligent I/O system, engineers are reducing panel space, wiring and termination points, and maintenance issues, while improving programming and configuration flexibility, and flattening control architecture.”

Commercially available products

Jerry Herman, new technology manager at Schneider Automation (North Andover, Mass.), points out that Schneider is targeting open networked I/O devices. The Momentum product line has communication adaptors for most industrial networks.

The truly open network, based upon commercially available technology, is Ethernet, according to Paul Bennison, Schneider’s new technology marketing manager. This is the network of the future for Schneider. Modbus is a network identified with Schneider, which is widely used in both discrete and process manufacturing. A product to be introduced at this fall’s ISA Expo/98 in Houston is a gateway for devices on Modbus to link to an Ethernet network.

Another company supporting Ethernet is PLCDirect (Cumming, Ga.). Tim Hohman, company captain, points to the benefits of Ethernet: proven reliability; fast speed that is getting faster; wide commercial availability of components; and, inexpensive price.

Control configuration options

Mark Knebusch, Phoenix Contact (Harrisburg, Pa.) Interbus group director, sees that customers have more options in how to configure control solutions. “Some customers want to concentrate the control into PCs, while others are looking to distribute control decisions into multiple networked processors.”

Phoenix Contact’s strategy, according to Mr. Knebusch, is to use Ethernet for controller-to-controller and controller-to-higher level communications and Interbus for virtually all lower-level communications. Interbus now permits TCP/IP addressing; so, a top-to-bottom communications system via TCP/IP is possible.

InLine is a new networking product ( Control Engineering International March, 1998, p. 89) from Phoenix Contact GmbH (Blomberg, Germany). According to Wolfgang Blome, president, “The most important task of Interbus is to connect systems, a task that does not end at the switch cabinet door. Phoenix Contact is bringing a total system kit, comprising switching, protection, control, and safety function, into the switch cabinet.”

Networked I/O’s benefits

“Typically, intelligent, networked I/O products are utilized in an environment requiring fast reactions to process changes through local decision-making,” notes Dennis Shreve, logic devices product manager at Cutler-Hammer/Eaton (Westerville, O.).

Adds Gene Stovall, Cutler-Hammer networking product manager, “Diagnostic information, which was previously unavailable in conventional control applications, is being increasingly recognized as valuable. The quantity and type of diagnostic information made available will continue to grow in scope.” Cutler-Hammer is adding DeviceNet capability to its sensor line, sending diagnostic information to the network.

Omron Electronics Inc. (Schaumburg, Ill.) offers products for DeviceNet, as well as its proprietary CompoBus/S network. Work on DeviceNet involves maximizing the number and type of I/O devices dropped from one node, with each node containing up to 256 I/O points. A new networking controller combines the reliability of a PLC with the flexibility of a distributed network system. According to Jeff Meyers, product marketing manager, “Proprietary systems are the only type that currently provide the level of accountability users demand. As the technology progresses, open systems will be able to provide the same level of performance and reliability.”

GE Fanuc Automation (Charlottesville, Va.) recently announced VersaMax I/O system that supports a variety of networks already on the market. “An intelligent, networked I/O solution may give performance far beyond conventional methods,” says Vince Tullo, vice president of the PLC business. “These systems are most effective when users apply many small groups of I/O clusters.”

Honeywell Micro Switch (Freeport, Ill.) has developed the Smart Distributed System (SDS), a CAN-based I/O network. Service and support manager Bob Nickels says, “It all comes down to managing bandwidth. The nature of the bandwidth information that is communicated is evolving to better meet customer needs for rapid configuration, simplified maintenance, and enterprise integration. Today, designers have moved the control logic into an intelligent SDS device eliminating the need to write and debug repetitive control programs at the PC or PLC.”

Make wiring easier

The development of open networked strategies has given opportunities for an expanded role in the market to several companies. Weidmüller Inc. (Richmond, Va.) originally manufactured terminal blocks. The product line has expanded into open I/O modules called Winblock.

据玛丽亚广场,魏德米勒网络I /O product manager, Winblock adds a lot of benefits to the original concept. Each I/O module has a communications chip built in and snaps on a DIN-rail mounted base. Maintenance personnel can hot-swap a module without bringing down the entire network or easily add new modules as required. Diagnostic information is now readily available to a central data collection point.

Wieland Electric (Burgaw, N.C.) also has expanded a terminal block and connector product line into a networked I/O module solution called Ricos. Engineering manager Greg Matthews sees a lot of interest for fieldbus networks like DeviceNet, Profibus, Interbus, and SDS. Demand is building for I/O devices compatible with these networks. People have inquired about the availability of Ethernet products, but little demand has been generated.

Mr. Matthews continues, “This technology allows engineers to gain control of the process by using smart devices for control at the process point. Error control and diagnostics are enhanced, and our Ricos product allows testing of the control before turning on the process.”

Bob Colburn, control products business unit manager at Grayhill Inc. (La Grange, Ill.), reports sales of Ethernet products have taken off fastest. He also sees demand for Profibus and DeviceNet.

Entrelec Inc.’s (Irving, Tex.) “Rio” product line was introduced to provide a solution to the various industrial fieldbuses in use today. Snap-in modules provide communications to Profibus, Interbus, and WorldFIP presently, and with other networks to come shortly. Product specialist Bryan Moore says that he sees much Profibus demand from customers along with DeviceNet. He also has had a few inquiries about Ethernet, but nothing concrete, yet.

Intelligent wiring

“The user expects fieldbus technology to be a practical application and easy to operate,” says Jürgen Volberg, Dipl-Ing with Klöckner-Moeller (Bonn, Germany). “The diagnostic capability is to be enhanced, and it must enable components to ‘plug and play.’ The number of terminals, I/O cards, and wiring bundles is increasing—and so are the costs for layout planning, engineering, and wiring. The answer is a fieldbus system which will reduce these costs.”

Mr. Volberg recommends the Actuator-Sensor-interface, known as the AS-i bus. He notes that the strength of AS-i bus lies in bringing about a reduction in wiring complexity. “AS-i adapts to the machine or installation, not the other way around.”

Addressing what is meant by networked “intelligent” I/O devices, Azam Owaisi, product marketing manager for Mitsubishi Electric Automation Inc. (Vernon Hills, Ill.), says, “In the past, when networked I/O was thought of, it was generally understood to mean mostly digital with some analog I/O modules. However, due to the complexity of user requirements, manufacturers are now offering a large array of ‘other’ networked products as well. Mitsubishi’s new CC Link (Control & Communication Link) network gives users networked high-speed counters, thermocouple, positioning, and other ‘intelligent’ modules.”

安德烈•Moldoveanu光尔格(弗吉尼亚州里士满)的销售and marketing manager, identifies three major benefits that are developing from current technology trends. “First, panels are out. The now-‘talkative’ I/O modules are moved down with the devices they connect with and the controller is packaged with the HMI. Second, junction boxes are out. They are replaced by watertight compact connector junction boxes. This development sparks the third: micro-automation centers. The easiest to recognize is the intelligent manifold, but coming is the intelligent motor controller.”

Rapidly developing computer technology is driving a host of new developments for the controls engineer. The goal of these new systems and products is to help get production processes commissioned more quickly, keep the process running for ever increasing lengths of time, and supply desired information to plant management so that informed decisions may be made.

This means that there is a lot of responsibility riding with today’s control engineers, but technology is coming to help.

Profibus automation

Wallace Inc.(Lisle, Ill.) has produced business forms since 1906. In 1990, the company decided to expand services to include warehousing and distribution of customer forms. This resulted in the construction of an automated 294,000 square foot (27,342 square meter) distribution center.

The original routing system consisted of a single gravity-fed roller-bar conveyor. Totes were placed on the system and manually pulled to each stock keeping unit for picking.

The tote was sent to a “sortation” area for weighing then transferred to a conveyor for shipping. A hand scanner read the bar-coded customer order document that traveled with the tote. The scanner was connected to a Simatic 535 PLC which connected to a personal computer. The PC communicated the information to an IBM AS/400 computer which returned shipping information to the line. This communication process took about two seconds.

不可避免的expansion

First a mezzanine was added in 1993 which more than doubled the number of SKUs to be picked. When a second mezzanine was required in 1997, Wallace decided the control architecture must be evaluated.

Conveyor supplier Conveyor Handling Automation working with systems integrator Numina Systems Corp. introduced a new concept called zone routing.

With the zone system, each tote placed on the new conveyor is married with a unique customer order resident on the AS/400. This is done with a bar-code label on the tote. The data stored on the AS/400 includes knowledge of where all the items are stored along the conveyor. When a tote arrives at a zone that has items to be picked, it is diverted for the picking process. This is done with standard bar code readers.

The conveyor travels at 90 ft/sec. At this speed, the system needed a means for handling data and making decisions quickly. Numina recommended individual micro PLCs to handle diversion decisions linked to a main PLC via Profibus-DP field-level communications.

Profibus benefits

Compared to the other conveyor systems at Wallace, Profibus-DP has several benefits. The “fieldbus” system allows a significant reduction in wiring. Each process cell has only one cable connecting to the main line. System performance is enhanced due to simplified information collection. The responsiveness of Profibus allows plenty of time to make a timely diversion decision.

Why Ethernet?

As control engineers make decisions that impact future control architectures, they must decide which bus to implement. The issues are many. Some decisions are technical, such as speed, determinism, node capability, and bus length. Some are supplier loyalty. And, of course, many are economic.

Once you choose a bus, your success is tied to the long-term success of that bus. At least seven different major bus architectures are vying to survive in the industrial automation world.

The networking standard is already established—TCP/IP over Ethernet. TCP/IP (transmission control protocol/internet protocol) was in the public domain, not driven by a single manufacturer or a consortium. TCP/IP and Ethernet are everywhere.

The combination of low cost, global familiarity, availability, and R&D investment assures continued success. With Ethernet, the ability for PCs, field devices, controllers, peripherals, and intelligent I/O devices to coexist on the same network is unmatched.

TCP/IP over Ethernet also unleashes the power and advantages of intelligent I/O systems. Intelligent, distributed I/O can now be Ethernet nodes that support higher level functions, such as counting, latching, totalizing, event/reactions, PID loop control, thermocouple linearization, and much more. In most device/sensor bus architectures, there are distinct lines between the enterprise level, host/controller level, and device network or I/O level. Each has its own tasks and functions, largely due to communication band width and available processing power. TCP/IP over Ethernet blurs those lines. Tomorrow’s control systems will blend the power of distributed intelligence with low cost, widely available technology.

Opto 22 has announced the addition of Ethernet connectivity to its Snap I/O product line.

Benson Hougland, director, technical marketing

Network on a chip

One of the factors propelling Ethernet acceptance as a control network has been the availability and reasonable price of PC components. Attaching sensor/actuator devices to the network is another matter. Osicom’s (Waltham, Mass.) NET+ARM chip changes that by making Internet TCP and Ethernet connectivity both inexpensive and easy.

NET+ARM provides not only the hardware needed for networking but also supplies fully integrated working software including the pSOS real-time operating system, drivers, and networking applications—all in one complete product offering.

Everything but the kitchen sink

The heart of the NET+ARM is a custom chip designed by Osicom and produced by Atmel based on the ARM 7 processor. Built into the chip are serial and parallel ports, a shared memory ENI (embedded networking interface), and a bus for connecting product specific control hardware.

Many application program interfaces are provided. HTTP (hypertext transfer protocol) is the standard web interface providing for presentation of HTML web pages to a user interface. File Transfer Protocol allows creation and transfer of data files. Mail protocol provides e-mail addresses with worldwide links.

More and more products today involve computing. Computer chips drive many industrial devices. The drawback to Ethernet in industrial devices has been the board size required for connection. By reducing that board to a single chip, Osicom provides an economical way for manufacturers to put devices on line.

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