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Most plant data collection applications use a batch approach, where data is transmitted at the end of the shift or other low usage times of day, but this is set to change.

New networking technologies will change this model to real-time, with plant information being continually and automatically collected and analyzed - without operator intervention. Plant operations will increasingly be directly connected in a client/server model to host computers and servers.

Controllers, PLCs and Enterprise Resource Planning (ERP) systems will be able to access any sensor connected to the control and device network. The result will be better information on manufacturing processes. Imagine the impact of every shop floor worker having the equivalent of a handheld, possibly wireless network browser at his or her disposal. In real time, process operators will be able to monitor and fine tune system performance, access plant information and communicate directly with their production line managers. These operational online continuous nodes will be another bandwidth consumer, raising traffic levels significantly.

And the network will not only supply information internally. Trends towards quick-response, vendor-managed inventory and electronic commerce, are demanding that manufacturing at the center of the supply chain be brought online. Customers and suppliers need to be able to look at all points in the supply chain, from initial order placement to raw material consumption to assembly to shipment and delivery.

Decision support systems and data warehousing applications will soon be able to "mine" massive amounts of data for correlation and trends that can lead to operational improvements. With manufacturing equipment and personnel on the network, higher management can have access to the operational data on the factory floor in unprecedented detail.

Fully Integrated, Single Information Base

The factory-floor, network-of-the-future integrates all company operations into a single information base. It will provide management with the most up to date data, enabling better decision making and improving response time. Table 1 shows how key business line functions correspond to plant information sharing and data communication requirements.

Table 1

Function	Information sharing / data requirements
Operations	Detail scheduling Sequencing, priorities, routings, shape, fit, setup, alternative / overlapping / parallel operations, equipment loading, shift patterns
Dispatching	Production units Flow, jobs, orders, batches, lots,work orders, sequences, changes,events, schedules, controls, buffers
Process management	Monitor, control, correct, decision support, tracking, alarms, tolerances
Product tracking and genealogy	Visibility, status, who is working on what components, suppliers, lots, serial numbers, environments, alarms, rework steps, exceptions, history, tracing, usage
Performance analysis	Up-to-the-minute status, results, history, measurements, utilisation, availability, cycle time, conformance to schedule, performance to standards, parameters, reports
Quality management	Analysis, measurement, collecting, quality control, identifying problems, correlation, symptoms, actions, results, tracking, inspection
Document control	Forms, instructions, recipes, drawings, standard procedures, programs, batch records, EC notices, as planned" and "as built"
Data collection/ acquisition	Interfaces, links, production/parametric data, forms, scanned transaction records, other collected data.

Technology Requirements

Complimentary technologies that support such network related business functions are many and varied. They include:

• Smart sensors and fieldbus devices. Electrical panels and intelligent circuitry in specialized local factory networks that enable multiple performance measurements on production line equipment, operations and materials.
• High bandwidth devices. Ethernet interfaces, data collection terminals, radio frequency (RF) devices/ transmitters and programmable controllers.
• Traceability. RF tags, barcodes and smart cards.
• Client/server installations & thin clients
• Internet access

Networking Between Two Islands of Data

Today, many devices are connected to a control network through proprietary serial cabling and protocols. Information is then consolidated from the control network running at speeds typically under 2Mbps. For this information to reach the corporate systems it must cross the divide between the control network and the information network with its links back into the enterprise office automation (OA) network. Typically, a PC based gateway or HMI workstation carries out this function. With interfaces to the proprietary control network on the one side and the Ethernet/TCP/IP based information network on the other, the gateway provides a route, albeit restricted, across the divide. In the majority of cases today, the information network uses 10Mbps shared Ethernet.

What's Driving the Move to Ethernet?

The first casualty of the information explosion will be the legacy fieldbus system with 2Mbps as its upper limit. Shared 10Mbps Ethernet will also be replaced initially by 10Mbps switched increasing to 100Mbps as need dictates. Ethernet will also extend its reach, driving the technology closer to intelligent devices and remote I/O. The Internet and modern networking designs will enable four major functions to be radically improved.

• Easier product installation for remote or local personnel using HTTP server and browser technology set up, re-configuration and status monitoring
• Diagnostics/repair help find and solve problems with device or devices' mission using SNMP, FTP, peer-to-peer or HTTP technology and memory dumps to host for analysis, download programs to RAM or flash memory
• Use the HTTP server to gather a wealth of information from a device
• Management reporting and network capacity planning

Comparing Industrial Ethernet with Office Ethernet

Industrial Ethernet and Office Ethernet differ from one another in the following metrics, see table 2.

Table 2

	Synergetic industrial ethernet products			Office ethernet products
	Hubs	Routers	NIC's
Operating temperature	0oC to +6oC	0oC to +60oC	0oC to +60oC	5oC to +40oC
Flame rating (UL)	x	x	x	Vendor Related
Multi-layer board for high noise immunity	Yes	Yes	Yes	No
Connector options	Screw-down DB-9, RJ-45, fiber	Screw-down DB-9, RJ-45, fiber	Screw-down DB-9, RJ-45, fiber	RJ-45
Redundancy (built-in)	Yes	Yes	Yes	No
Industrial enclosure	Yes	Yes	N/A	No
Electrical	24V DC	24V DC	N/A	110V AC
Guaranteed backward compatibility, 10 years	Yes	Yes	Yes	No

Conclusions

Industrial Ethernet is a viable networking alternative for most industrial applications. As with most networks, the control and/or systems engineers must rigorously test it, along with its many alternatives, in order to determine whether or not it is the best choice for a given application.

This article is reproduced with kind permission of the Industrial Ethernet Association.