Commercial technologies and business needs continue to propel human-machine interface (HMI) software. Only a few years ago, HMI software provided graphical representations of PLC data to enhance operator information. Software development has meshed with corporate needs to enable greater functions that assist made-to-order manufacturing with ever-shrinking inventories and lead times. Web technologies are driving this software to meet new challenges.

HMI software as a category of automation products is undergoing constant change. Only a few years ago, operator interface (OI) costs were just a fraction of total automation costs. OI consisted mainly of pushbuttons, pilot lights, and LED displays with either serial or proprietary communications protocols. DOS-based graphics displays only made inroads into factories in the past 10 years.

Graphics displays combined with data acquisition software bred a genre known as HMI/SCADA. Each company participated in the race to add drivers, so each package could read data from other companies' controllers. Software moved to Microsoft Windows platform, using technologies like cut-copy-paste, drag and drop, DDE, and multiple open windows to enhance functions. Increased functions led to increased complexity and cost.

Automation interface software today combines traditional operator interface, process visualization, data acquisition, and alarming, with enterprise solutions based on real-time manufacturing data communicating from controller to corporate systems and back. These products accomplish more than interfacing machines with humans-they interface real-time information from automation systems with anyone or any system requiring that information.

Mitch Vaughn, chief software technologist at USDATA (Richardson, Tex.), believes more changes are coming. 'The whole web technology idea will eventually replace HMI as a product. It used to be just textual transactional, but now it is very graphical as well as interactive. That sounds just like HMI. SCADA components like data collection, alarming, etc. are moving to a higher level functionality within business. We now use web technologies not just for visualization, but also for control.'

Is use of web technologies something coming from suppliers down to users? Bob Thaler, Intellution's (Norwood, Mass.) director of product marketing, says, 'Customers from every manufacturing area we serve have asked for a browser-based solution, especially for users who have only occasional need for manufacturing data and visualization. Another reason is e-manufacturing emphasis, where legacy and new systems partner to enable faster reactions to market demand and customer needs.'

Incorporating web technologies can mean a change in HMI architecture. Older systems use a proprietary display connected to a one controller or PLC. Over the last five years, a type of client-server architecture has evolved. Now known as thick client or rich client, it uses a PC as a server housing the main application program and central database. Clients run a reduced version of the application and are distributed around the plant.

Web technology involves a server and a browser. The server stores information, currently in the form of 'pages' and, soon, in database fields. A PLC can be a web server; for example, Schneider Electric (North Andover, Mass.) has embedded servers since 1998. Browsers are typically free of charge. Microsoft Internet Explorer is part of Windows. Netscape Navigator is a free download from the web. Espial (Ottawa, Ontario, Canada) makes Escape 4.0, a Java-powered browser for PCs and embedded applications. Browsers read and present server information, so a browser connected to a web-enabled controller presents operator interface graphics and information.

Even though browsers run on very small devices, like Windows CE computers, an application-the browser-is still required. Thin client, another HMI architecture, requires almost no software. All processing, including graphics, is accomplished on the server. Some tout the benefits of client-server multiprocessing; others, thinclient for a single-application site.

Ralph Rio, GE Fanuc Automation's (Charlottesville, Va.) Cimplicity marketing manager, suggests, 'Segment casual users from continuous users to determine appropriate architecture. Continuous users, typically found on the factory floor, might be better served with a thick client. They often must do control as well as display information. Casual users do not need full applications. These users, typically engineers, managers, or cost accountants monitor or occasionally troubleshoot systems. They need something to turn on, connect, read, and leave. A sliding scale of architectures from browsers to thin clients perform well here.'

Another way to look at architecture is the proliferation of display devices. VenturCom (Cambridge, Mass.) provides real-time foundations for various manifestations of Windows operating systems. Typically concerned just with controllers, Roy Kok, VenturCom's vp, notes, 'Moore's Law has worked to the extent that small, embedded, single-purpose devices are now powerful computers with lots of memory. That's why you can put a browser in a small piece of equipment. Our focus now is not just on devices but on connected devices. In fact, our focus can now be stated as providing products and services for intelligent connected equipment.'

Looking at browsers and embedded non-PC device development, Mal Raddalgoda, senior director strategic marketing for Espial, notes, 'There are two dynamics at work for similar reasons. One is the web, and the other is Java. The reasons are portability of the user interface (UI). If the information is web-based, it can be browsed anywhere. Java programs can be run anywhere. We see increasing demand for portability and universal access to information. These technologies satisfy that demand.'

'eMation' (formerly PC Soft International, Mansfield, Mass.) builds on these technologies. Explains Jim Hansen, senior software architect, 'We use browser-based operator interfaces enhanced with Java. It's a way of letting operators know what's going on with equipment, but the operators don't need to be right there at the equipment site. Java allows us to expand OI to nonPC devices, like new web-enabled cell phones. XML is a new web standard that allows data exchange. We're building products to use it in the enterprise setting that will put it to business use.'

Another two standards that have propelled Internet and web expansion are FTP and HTTP (see sidebar). These protocols are device and operating system independent. They allow users to download files and configured pages from remote servers. Naturally, automation interface software uses them.

'Our web-enabled PLCs have HTTP and FTP servers embedded with a default set of diagnostic web pages and Java applets. Users view run-time data directly from any standard browser on any piece of hardware-hand-held device to PC,' notes Christopher Martin, Schneider Electric's senior product marketing manager. 'Benefits extend far beyond just cost and encompass reduced learning curve on new equipment due to consistent look and feel. OEMs benefit when just one trip to a customer site is eliminated to solve a simple problem by the ability to dial up and view the problem.'

Ask what the most-used feature of the Internet is, and the answer will certainly be e-mail. Jeff Meyers, Omron Electronics' (Schaumburg, Ill.) product marketing manager, says, 'Our embedded e-mail client sends data, memory, or messages to an SMTP mail server. The OI can be a pager, PDA (personal digital assistant), computer, or other e-mail client based on triggered times or events. Network traffic can be significantly reduced with this technology.'

ActiveX is really a Microsoft technology built on Object Linking and Embedding (OLE). It enables objects like sliders, push-buttons, or digital displays to be embedded in a document like a web page, providing a useful web technology.

Ganesh Ranganathan, Lookout manager for National Instruments (Austin, Tex.), notes, 'Our HMI software uses ActiveX technology for web interface. Users can monitor and control processes over a standard web browser. Knowledge of XML or HTML is not required. No additional software is needed on the client.'

Many voice concerns about security when using web connections. Mr. Ranganathan explains, 'We enable tight security. The Lookout server checks for security levels of web clients accessing it. Specific access privileges are required for ability to control switches and pots.'

What if many graphics screens already exist that would be costly and time-consuming to convert to web-based display? Dave Hancock, Automation Control Products' (Alpharetta, Ga.) vp, has an answer. 'Graphics pages converted to web screens may not look and work like the original screens. On the other hand, no modification is required to move the same screens to a thin-client system. The same software and user drawings that run on Windows NT 4.0 will run on thin clients.

'To make a thin client work,' he adds, 'a small application runs on the client to receive graphics commands from the server and package and send user inputs back to the server. Actually, while most thin client solutions use greatly simplified hardware, a full PC can also be a 'thin client.''

Makers of traditional HMI software also recognize this problem. Steve Morales, HMI product manager at Siemens Energy & Automation (Alpharetta, Ga.) notes, 'Customers desire a diskless client, often running Windows CE. We have Web Navigator that runs HMI as a client through a browser. It converts screen captures into to a file transportable over TCP/IP. This provides a single database and point of entry for maintenance.'

'A useful technology for data exchange is OPC [OLE for process control],' Mr. Morales continues. 'WebOPC accepts information as an OPC client and packages it in HTML pages.'

Microsoft has a technology called Active Server Pages (ASP), originally part of Internet Information Services (IIS). It provides for creation of dynamic web pages. According to Rockwell Automation's (Milwaukee, Wis.) HMI business product manager, Daryl Walther, it saw the benefits some time ago, releasing ActiveDisplay almost two years ago. This product requires client application software. For those who wish a pure browser solution, the company's new WebServer product allows transport of static HTML pages viewable with a standard browser.

Mr. Walther notes, 'Users want the ability to get data where needed. Often that place is not near the machine or process. An engineer may need to view the process from a remote location and communicate with on-site maintenance personnel.'

Another way to provide an entry for legacy systems to the web, according to Advantech Automation's (Cincinnati, O.) product manager, Mike Rothwell, is a small PC terminal with software that allows user-defined host web page development. Connectivity to PLCs and Ethernet for Inter/intranet allows clients with browsers to get real-time updates.

Shimon Nurick, P-CIM manager at Afcon (Schaumburg, Ill.), says it's no secret that the web is an inexpensive and practical alternative to traditional client/server architectures. 'Tool development for web-based applications cannot keep pace with fast-changing technology,' he adds. 'A software package like ours repackages application changes and downloads them with the next connection of the user's Internet Explorer.'

Fred Putnam, Labtech's (Andover, Mass.) ceo, believes its Internet Explorer and Netscape plug-ins in 1996 were perhaps the first web-based HMI. He adds, 'Besides the ability to control remotely, our users asked for a system they could configure themselves, without having to deal with HTML, or even involve their IT professionals. NetMMI delivers this. Open interfaces such as OPC, DDE, VB [Visual Basic], and DLLs are crucial for users' ability to construct a complete system.'

Rapid technology changes and business requirements are forcing HMI/SCADA software to incorporate visualization and data aggregation and move beyond furnishing the 'missing link' of real-time manufacturing data piped directly to decision makers. Business today requires rapid manufacturing response to market demands. Web technology is a valuable tool for control engineers trying to keep up.