Windows-based PCs are becoming an important part of the industrial world, controlling manufacturing and other operations while feeding back data in real time for analysis and decision-making
Mark Clarkson
Things are changing on the factory floor. In the beginning, there were PLCs (programmable logic controllers), metal boxes packed with jumper wires and chattering relays, and they were good. Well, pretty good. If you wired enough of these boxes in exactly the right way, setting the relay jumpers properly, you could program them to handle the types of quick, repetitive tasks involved in stamping airplane parts out of sheet aluminum or filling and capping bottles of root beer.
The user interface for one of these beasts was a large metal panel called an enunciator panel, cov
ered with cryptic gauges and industrial-size buttons in primary colors. The programming language, if you could call it that, was relay ladder logic. It was implemented by physically yanking and rearranging jumper wires to govern the sequence in which relays were tripped by sensors and other relays. Over the years, the industry accrued a large base of electricians and production engineers who spoke relay ladder logic; even as microprocessors replaced the relays inside PLCs, relay ladder logic was still used to program them.
Then, as now, PLCs governed mostly discrete processes--the mechanical actions found in stamping parts, folding boxes, or running vending machines. To control more-subtle analog processing, such as the distillation of huge vats of petrochemicals, there were DCSes (distributed control systems). Typically, these DCSes were operated from a single control room, isolated from the shop floor, and attended by a priest-like order of engineers and electricians. From this control room, lines sn
aked all over the plant, gathering information and sending orders.
The requirements on the factory floor are changing fast, says Gary George, director of marketing for Opto22, a maker of industrial-control systems for PCs. ``People now want to talk to third-party devices like bar-code wands, intelligent scales, and gas analyzers--things that DCS and PLC weren't designed for. People want integration, and these older architectures are only going to take you so far. The real future of control is the computer.''
A Matter of Trust
When small computers first began to appear on, or near, the shop floor, they were not trusted to do very much. Early computers were notorious for all kinds of failures. At first, all they were used for was to replace those big panels of buttons and dials on the shop floor with on-screen representations of buttons and dials. Even that represented some big cost savings.
``You'd be surprised,'' says George, ``at the cost of building those enunciator panels--the m
aterials themselves, plus the cost of someone putting in push buttons, pulling wires, and assembling the panels. Now all that stuff is done in software. Now, you use a touchscreen or a light pen.'' To change the process, continues George, ``you only need to go in and create a new window or move a gauge from here to there. There are no rewiring costs.'' In the control industry, this is known as MMI (man-machine interface). Running MMI software is still the major function of PCs on the shop floor.
A PC running MMI software is probably not actually turning on pumps or opening and closing valves. According to George, traditional control elements, such as PLCs, still typically perform those tasks. What MMI offers is a new and better way of talking to those traditional control elements. If a valve opens, the computer may turn an icon red. If you click on a button, the computer tells the PLC to start or stop a process.
Even though the PLCs are still there, you can program them through the MMI. Today's
programming languages are much easier to use than relay ladder logic. For example, Opto22's programming language is based on flowcharts. People understand flowcharts, says George. ``They're intuitive. We go right from the flowchart into the controller. It eliminates a whole step in the programming.''
Real Objects
MMIs have grown far beyond cartoon enunciator panels, although the emphasis on modeling physical hardware in the real world has remained. Today, a typical MMI display looks like a factory diagram drawn in Harvard Graphics, with colorful cartoon fluids pouring into cutaway vats or streams of widgets rolling down animated assembly lines. Lights wink on and off, numbers change, and gauges fluctuate. (The screen shot to the left shows examples of this.)
The best MMIs are strongly object-oriented. You can move, duplicate, edit, and copy objects (e.g., gauges, vats, and conveyer belts) on the screen from application to application. When you copy or move objects, their characteristics a
nd behavior go with them. If you copy a picture of an industrial cookie-dough mixer, you get the whole element (e.g., timers and animated beaters). If the second mixer differs from the first, you can edit only those characteristics that differ between the two.
The latest MMI software from Wonderware of Irvine, California, for example, lets you build libraries of complex, animated objects such as meters, valves, and pumps and configure them quickly in the shop environment. Dave Smith, Wonderware's vice president of marketing, says that an object that took you 20 to 30 minutes to configure before will now take only 20 to 30 seconds. If you have a meter with a scale of 0 to 100, and you need a scale of 500 to 5000, you simply click on the drop-down box, change the scale, and create a new object. This can save much time in programming the control system for 53 similar vats of acid or similar manufacturing stations at a dozen different locations in your plant.
``People on the factory floor,'' says Sm
ith, ``would like to follow the process as it really operates--to see tanks filling, valves opening, pumps pumping, and so forth. Instead of looking at numbers, they'd like to see a tank being filled and to see an alarm change color when it reaches capacity.''
And that's the big difference between MMI and presentation graphics--objects in the MMI represent real objects in real time. MMI software is object-oriented in the most literal sense. For every animated vessel that is 58 percent full of cartoon petrochemicals, a real vessel exists that is 58 percent full of real petrochemicals.
Power for the People
Outfitted with slick new click-and-drag animated interfaces, industrial MMI is going places it's never been before--most significantly, out onto the factory floor. In the past, engineers and technicians programmed controllers. Today, thanks to sophisticated MMIs, many people on the shop floor who have never worked directly with computers are doing the programming themselves.
When d
ealing with such novice programmers, ease of use is a premium. ``For the latest version of our MMI software,'' says Ralph Rio, manager of product marketing for Intellution, ``the design objective was to enable a new user to go from opening the shrink-wrapped box to being truly productive within one hour. And we've done tests to make sure we achieved it.''
Once users are comfortable with the new technology, companies begin to derive benefits they never expected. Companies shopping for automation-control software are initially interested in improving yields, reducing waste, or making processes more effective. They get those things, Rio says, but the real benefits come from empowering the workers. ``Typically,'' he says, ``the person on the production floor is not empowered at all. They're put in front of a machine and told to push a button every so often. They don't have the information needed to make high-quality decisions. By giving them information in a usable, digestible form, you empower them.'' Rio
adds that this does more than make them feel good; it makes the companies they work for stronger.
He cites an example from an Intellution customer. ``A guy on the plant floor--in his 50s, high-school education, not a computer jock at all--learned to use our software and started drawing his own screens, because he wanted to see the information a little differently. He found a relationship between things that were happening in the production process that no one had seen before. It turned into a $250,000-a-year cost savings for the manufacturer.''
Windows onto Factory Automation
From the beginning, Windows has been the platform of choice for PC-based industrial MMI. As a graphical operating environment, early versions left a lot to be desired. Still, says Smith, Windows had one important thing going for it: It didn't tie you to a specific brand of hardware.
Until five or six years ago, companies providing hardware and software for industrial-process control dealt in proprietary syste
ms. Each system spoke its own particular language, and it was hard to incorporate other product lines. The manufacturer was often the only source for maintenance, service, parts, and programming. Once your company made the commitment to a particular line of products, you were stuck with them for a while.
The result was captive markets and high prices. Until recently, says Smith, control-system suppliers were paying $50,000 to $100,000 for a hard-wired graphics workstation. The PC has pretty much put an end to that by offering the industry something it's never had before: open architecture--a ubiquitous, open platform for developers of both hardware and software. Nowadays, there are scores of companies selling cards that plug into your PC to program, communicate with, or replace current control systems. A small but thriving software industry is growing around PC-based industrial control.
Even better, PCs are produced by the tens of millions all over the world. By investing in PCs, the industry, t
oo, can reap the economies of scale, replacing those $50,000 graphics workstations with $2000 PCs. If someone invents a faster parallel port or a bigger monitor, you just buy one and plug it in. And Windows offered a relatively ubiquitous GUI for the PC.
In addition to graphics, Windows offers one other tool that has proved essential: DDE, which Windows applications use to pass data back and forth as they run. Software can use DDE to take data from other programs or, with the proper drivers, from hardware such as network cards, serial ports, and PLCs. Industrial-control programs send and receive their data via DDE.
``The beauty,'' says Smith, ``is that customers can use those same DDE servers to move data into other Windows applications, such as Excel. They love the opportunity to do that.'' By wrapping DDE drivers and interfaces around other systems (e.g., VAXes), you can make their data available to the PC without having to do a full-scale port of your software to those other systems. To facil
itate moving this data around, Wonderware wrote a network version of DDE, called Net DDE, which it subsequently licensed to Microsoft for use in Windows NT.
Speed Bumps Ahead
Anyone introducing new technology into an existing factory must be prepared to integrate it with an array of preexisting legacy hardware, both dedicated control systems and minicomputers--the latter consisting largely of DEC VAXes running VMS and Unix. ``Corporate America,'' says Smith, ``has a huge investment in these systems, not only in terms of the hardware but also in terms of the software written for those environments. They won't give that investment up easily.''
Windows often serves as a universal client, letting users implement complex multiple-system solutions including PC, VAX, Unix, and DCS systems. The PC stands, like the robot C3P0 in the movie Star Wars, as a translator between human and machine--and sometimes between humans and other humans--fluent in the myriad languages and dialects of the industria
l-control machines. Factories can migrate toward less expensive distributed PCs at their own pace, without throwing away the millions invested in their older control systems.
Once you have linked these disparate systems together, they still require some sort of common language to talk to one another. SQL is the lingua franca of the database world. Given sufficient fluency in SQL, a program on your PC can access data from mainframes, minicomputers, and other PCs. Effective industrial-control software must speak SQL. On the PC side, ODBC (Open Database Connectivity), a nephew of SQL, is fast becoming important as well.
SCADA
Once you've started to implement a distributed system of PC clients and assorted hosts that are networked together and can speak to one another, the implications are enormous. Consider the lowly statistician, toiling away in a cubicle, analyzing data. To gather the data, he or she may have walked down to the factory floor and taken samples off the line or may have taken
it from periodic reports issued from the factory floor. In any event, the data is cold. The statistician is not seeing the process as it's happening now but rather as it was in the past--several hours or several days ago. Now he or she must enter the data into a statistical program and study the resulting graphs.
Consider the statistician's boss, who waits for the analyses. By the time he or she gets it, the data is colder still. Consider the contract-process engineer, who works on the opposite coast, trying to fine-tune a process he or she's never seen running.
Now, give each of these people a PC plugged into the company network, with graphical software that shows the process running in real time. Let them redesign the screens, just like the industrial MMI users, to show the data they need the way they want it. Provide them with statistical control charts that update in real time. Add software that tracks inventory across the shop floor, that will show you where every component of a given orde
r is and in what stage of completion at any given second. Make some of these PCs read-only, allowing certain people (e.g., accountants) to watch a process without being able to meddle with it. If people along the line speak different languages, say Spanish and English or German and French, then you should provide each user with data in the language of his or her choice. State-of-the-art software does all this.
Traditionally, this type of high-level software is known as SCADA (supervisory control and data acquisition). On the PC, the distinction between SCADA and MMI is ceasing to exist. Many vendors service both areas with a single, reconfigurable product.
Bigger, Better, Faster, and Safer
Windows may be a well-accepted graphical interface, but it has never been a paragon of stability. A general protection fault at the wrong time can crash your whole system, and a crash on the shop floor can be very costly. ``People in the office may not like it when a piece of software burps,'' says Smit
h, ``but they're more forgiving than the guy who's making a million dollars' worth of chocolate.''
Also, industrial MMI is driven on real-time data, and Windows makes a lousy real-time environment. The smallest resolvable clock-tick is too large for finely timed processes. Even worse, Windows is a shared, multitasking environment that relies on every application behaving politely and not hogging resources. If a database takes an extra few seconds to close its files, other applications must wait in line. In the industrial-control environment, those seconds can mean disasters ranging from a ruined batch of cookies to a melting nuclear core; that's just not acceptable.
In the past, vendors of industrial-control software were forced to ``fix'' Windows to achieve the performance and reliability they needed--writing patches and DLLs or hacking into Windows' multimedia drivers--or they had to use a less widely accepted operating system. But evolving operating environments and faster processors promise
some relief. NT and the upcoming Chicago are slated to provide a more robust, fault-tolerant environment with true preemptive multitasking--something an industry weary of patching and tweaking sorely needs.
In addition, the new generation of microprocessors (e.g., Pentiums, Alphas, and PowerPCs) will make everything go faster in general. This will be a big boon to developers trying to make their products work successfully in real time.
As PCs become faster and more stable, they're winning the trust of the industry. Although there will probably always be two-box systems with dedicated PLCs controlling the machinery and PCs providing the interface to humans, more factories are giving over control of their manufacturing processes completely to PCs.
``We recommend that our customers use our software to actually control the line,'' says Intellution's Rio; ``we're that confident. Our software runs in many mission-critical applications, including controlling nuclear power plants, so it's certain
ly safe to use it to make cookies.''
Automated Process Control
Industrial-control software is showing up in areas far from the factory floor. Opto22 is wiring up the East German city of Leipzig (population 650,000) for the local water utility. The system has thousands of data points with multiple remote links, and it's all handled with PCs.
Industrial MMI is being used in security and climate-control applications for museums, banks, and prisons, which might have thousands of sensors of all types. While a typical home-security system is fairly dumb, systems with thousands of components require considerably more intelligence--if for nothing else than dealing with the inevitable failures. ``When you have thousands of sensors,'' says Rio of Intellution, ``it's a lot more likely that one will go off accidentally. So the system might look for groupings of two or three alarms going off at once and then call the police,'' Rio adds.
Wonderware's software controls rides at Walt Disney World
and monitors the worldwide flow of money for one Federal Reserve bank. ``We realized a few years ago,'' says Wonderware's Dave Smith, ``that this isn't about industrial MMI anymore. This is about getting real-time data from point A to point B, so you can make real-time decisions that affect your business.''
Illustration: This sample screen shows off some of the interesting kinds of graphical representations that can be used to monitor industrial processes with Opto22's MMI software.
Illustration: This model of a gasoline engine, showing valves, pistons, and spark plugs in motion and carrying out their functions, was created with the Wonderware MMI, using complex, animated objects.
Illustration: The application of MMI tools in a somewhat different direction resulted in creating this chart showing historical trends in a manufacturing process. It, too, was created with Wonderware's product.
Mark Clarkson is a freelance science writer livi
ng in Wichita, Kansas. He can be reached on the Internet or BIX at
mclarkson@bix.com
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Process Control's New Face
