Article - September 2002
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Web-Based Control Systems - Doing more with more


Steve Tom, PE, PhD, 
Director Technical Information
 Automated Logic Corporation

More access, 
more flexibility, 
more interoperability, 
wider area integration, but not 
more cost. 


Let me begin by explaining the subtitle "Doing more with more." This article is about ways in which a web-based control system can enhance your facility operations. Web-based systems can provide more access, more flexibility, more interoperability, and can provide these benefits over a wider area than conventional control system. Thus, the common phrase "doing more with less" doesn't apply here. Web-based systems give you more; they just don't have to cost more. Since everyone seems to have their own definition of what a web-based system is, let me state my definition at the outset. A web-based system is one in which the primary user interface is provided through web pages which are accessed on a standard web browser. Monitoring conditions, running reports, changing setpoints, changing schedules, receiving and responding to alarms, downloading updated control programs and graphics - all the typical activities an operator may do on a day-to-day basis are handled through a browser. There may be other tools for offline preparation of major engineering changes, creating new graphics, etc., but there is no "operator workstation" other than the browser interface. A "web-enhanced" system, on the other hand, still uses a conventional operator workstation as the primary operator tool but provides some features through a web browser. As you might have guessed, a web-enhanced system will provide some, but not all, of the benefits of a web-based system. Both will provide more access, more flexibility, and more interoperability over a wider area than a conventional control system. How do they do this? Let's look at these benefits one at a time:

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More Access: Conventional control systems require special software to be installed on each operator workstation. The primary workstation or workstations are typically located in a maintenance office, which can range from a high-tech 24/7 operations center to a salvaged desk in the corner of a mech room. Additional copies of the workstation software may be installed in other locations - the maintenance superintendent's office, the facility engineer's office, a laptop computer that the on-call technician takes home with him, etc. The number of these workstations is limited by the fact that workstation software is not free, and few customers can afford to install this software on every computer that might be used to access the system.

A web-based control system, on the other hand, only requires special software to be installed on a single computer, which becomes a web server. (Multiple computers can be used for system redundancy, but conceptually it's still a single computer.) This server generates web pages that serve as the user interface to the system. Any computer with a standard web browser can be used as an operator workstation. This means all of the computers listed above, and many more that weren't listed, can be used as an operator workstation if you allow it. (For security reasons you may want to restrict the computers that can access your system, and you will certainly want to restrict the people who can log in, but that's another topic.)

How does this increased access allow you to do more with your system? By allowing everyone who has a legitimate need to work on the system to do so, from whatever location they wish, at any time of the day or night. The facility engineer, the maintenance superintendent, and the maintenance technician can all access the system from their office, from their home, or from any other computer they have access to. The office administrator can access a restricted portion of the building, say, to adjust the schedules and temperatures in the Engineering Offices. The Shipping Foreman can have similar privileges in the Shipping Department. Letting people control their own departments gets you out of the business of running a call center for minor temperature adjustments, but of course it doesn't mean you abdicate your role as the energy manager. You can see every change they make, set limits on their adjustments, and monitor departmental energy use. If your facility is too small to justify a full-time energy engineer, you can hire a consultant who can use your web-based system to analyze your energy use and improve your operations from the comfort of his office - even if that office is on the other side of the world.

Sidebar on Web Services

Web Services will greatly simplify computer-to-computer transactions. Some experts are saying they will prove to be much more powerful than anyone yet suspects, just as the PC turned out to be more than just a smaller version of a mainframe computer, or the Internet proved to be more than just a better way to run an electronic bulletin board. However, one problem that may slow the growth of Web Services is the lack of standardization of the data that is being exchanged. Web Services provide a standard way to locate and gather data, but if every computer application has a different data model, the data may be of limited use. This proved to be a problem in some of the early Internet based business-to-business transactions that predate Web Services. XML provided a universal way to format the data, but if the data structures used by the two systems were fundamentally different there was still a lot of hand coding required. One suggestion has been to develop "vertical standardization," that is, standard data models within each industry. A data model that works in the Electric Utilities industry would probably not fit the needs of the Real Estate industry, but standardization within the utilities industry would make it much easier to develop a Web Service that would work with multiple utility companies. Great in concept, but where would such a standard come from? ASHRAE's BACnet committee would might be a good starting place, and they have discussed an XML extension of BACnet which could be used with Web Services. Perhaps a question that needs to be answered first is, "If the dream of Web Services were to become a reality, and you could exchange data with any other computer system in the world, how would you use this tool to improve your building automation?" Share your thoughts on this question in the Web Services Forum at

More Flexibility: Because standard web pages are used as the operator interface, any "gadget" that surfs the Internet can be used as an operator workstation. Certainly any Windows PC or laptop can be used, but the choices are wider than that. Mac users surf the Internet. So do Linux users. Many cell phones and personal digital assistants can surf the Internet as well. Your building automation system may need to generate special web pages for the small screens on these non-PC browsers, but that's not a problem for a well-designed web-based system. Conventional building automation systems have long been able to buzz a pager when something goes wrong in your building. With a web-based system you can now use a cell phone to respond to that page, browse the system, and make whatever changes you want, from wherever you are. If you happen to be at a movie when the page comes in, you can make these changes without leaving the theater. (If the plot gets a little slow you can even call in on your own, just to see how things are going.)

The advantages of wireless communication are not limited to cell phones. Wireless Ethernet transmitters and receivers are a low-cost way to give roaming access to a technician's laptop anywhere in your building. Ever listen to a radio conversation between a technician on a ladder, looking at a VAV box, and his buddy sitting at an operator workstation? "OK, open the damper. Is it open? Try closing it. You sure you're on the right VAV box? No, I said I was across the hall from the conference room. Now try it. Is it open?" etc. etc. With a web-based system and wireless Ethernet, the technician on the ladder can test the system himself, without all the confusion and delays of the radio calls. More importantly, his buddy is free to do something a little more productive than sitting in front of a computer screen, pushing buttons on command.

More Interoperability: The use of Internet standards makes web-based systems interoperable at the hardware level. To those of us who don't have our heads in the Ethernet these standards may be a confusing "alphabet soup" of acronyms - TCP/IP, HTML, XML, WML, HTTP, IEEE 802.11b - all of which ensure web devices can connect to one another. The WAP cell phones, standard web browsers, wireless Ethernet networks, and similar technologies already described would not work without these standards. Simply connecting devices does not guarantee interoperability; however, any more than the phone on my desk guarantees I can communicate with people in China. That phone can connect me to a telephone in China, but if I want to communicate I'd better learn to speak Chinese. The same concept holds true for building automation systems. The Internet standards inherent in a web-based system ensure connectivity, but for true interoperability the system also needs to use a standard "language" like BACnet. BACnet allows equipment made by different vendors to talk to one another over the communication channels provided by the Internet or a local intranet. Before BACnet it was common for HVAC control vendors to create custom translators or "gateways" to connect their system to a chiller, a boiler, or some other isolated piece of equipment. BACnet eliminated the need for the custom translators. Now the building automation system can talk to the equipment directly, and what's more, it can talk to a building automation system made by a competing vendor. Configuration tools like "auto-discover" make it possible for a programmer or a knowledgeable end-user to see what information is available in the other system, and to establish new links between systems. These links are not limited to just exchanging point data, either. BACnet includes high-level system functions, like scheduling, alarming, and trending, which make it possible to manage the entire system from one vendor's workstation. Combining a powerful language standard, like BACnet, with the connectivity standards of the Internet, makes web-based systems very interoperable.

The use of Internet standards is also bringing a new level of interoperability to building automation - one that will extend well beyond the physical plant. A new class of applications called Web Services will make it possible to link a building automation system with other computer systems on the Internet. This would make it possible, for example, to use weather forecasts and real-time utility prices as inputs in the control algorithms for your building. Similarly, a tenant billing system could query the building automation system about hours of operation, setpoint adjustments, or metered energy use. These types of interactions are possible today, but only if you're willing to invest the time and money required to develop a custom application to link the two computers. Web Services will expedite this process, providing tools to discover which computers on the web have the information you need, tools to extract the data, and a standard format for the electronic data exchange. Since web-based control systems are already on the web and are based on Internet standards, Web Services are a logical way to enhance their interoperability.

[an error occurred while processing this directive]Wider Area: The benefits that web-based control systems bring to a wide area operation are staggering. The World Wide Web is by definition the widest area network on the planet, and web-based systems are designed to operate over the World Wide Web. National retail stores, hotel chains, large corporations, and government agencies can exercise better control over their far-flung facilities by utilizing the web. Detailed energy analysis, fault detection, 24-hr alarm centers, and similar functions which could not economically be implemented in each individual building become very attractive when managed over the web. School districts, university campuses, medical centers, and others who manage facilities within a smaller area have long used conventional control systems to provide this centralized control. For them the benefits of a web-based control system are that it uses the networks they already have in place, without requiring a special facility network or dedicated phone lines for dial-up access. Even a small family business with a single facility can benefit. For them, "wide area access" means they can check on their building from home and receive alarms through their home computer if anything goes wrong after hours.

Of course, the idea of putting your facilities on the web does raise security concerns. There are a few people surfing the web whom you most certainly do not want accessing your building. In this, you are not alone. Banks, hospitals, government agencies, military units - there are many organizations who depend on the web for day to day operations but who don't want to share their data with anyone who stumbles across their URL. Fortunately, there are many tools to safeguard data on the Internet. Firewalls, Secure Sockets Layer, Virtual Private Networks - the details of these security provisions are beyond the scope of this article, but suffice it to say that they are sufficient to protect the sensitive data of these users. Chances are, "hackers" are much more interested in this data than in your setpoints and schedules, but it is comforting to know that you can have the same level of protection as these high-threat targets.

More access, more flexibility, more interoperability, wider area integration, but not more cost. There are many more ways in which a web-based control system enables you to do more with more, but this is a start. The exciting part is that this is not a "pie in the sky" prediction of things that might be. There are hundreds of web-based control systems in use today, and they are living up to their promises.

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