Abstract

Perhaps no other technology has had the profound impact on virtually everything we do than the Internet. It is changing the way we make purchases, the way transactions are conducted between businesses, the way in which we obtain information, and the way we communicate with one another. This article discusses how the power of the Internet is being adapted to real-time control and automation systems.

Background

Protocols - Over the last several years, most manufacturers have adopted one or both of this industry's leading open communication protocols: BACnet and LonTalk. The development of control hardware using these protocols is providing customers with options and solutions that were not possible with proprietary communication protocols. In addition, Ethernet is becoming the dominant network solution and is being used in more applications at lower levels in system architectures every day.

[an error occurred while processing this directive]System Architectures - Most of today's control and automation systems use a client/server architecture. In this architecture, each system typically has a server where data from the system is concentrated and "served" to clients accessing the system. The software running on the server is usually a manufacturer's proprietary application, as is the application running on the clients and the protocol it uses to pass information between the server and its clients.

The Internet - Recently, several manufacturers have announced plans to allow access to their systems from a standard Web Browser. While this certainly "frees" an end-user from the traditional proprietary client software packages found in most of today's system architectures, it should not be confused with providing a true Internet-based open control system solution and all of the benefits that such a system can provide.

Expanding the Possibilities

What about expanding the concept of an open system? What if we could take these increasingly popular open communication protocols for control hardware and bring them together with the power of Ethernet and more specifically, the Internet? How can we leverage the large installed base and the economies of scale provided by IT industry technologies and utilize them to deliver lower cost, open control solutions? How can we enable control companies and system integrators to deliver cost effective integrated solutions to the customer?

The answer lies in creating an infrastructure that marries the open control protocols, such as BACnet and LonTalk, with the standard protocols and data exchange formats that exist in the IT world today. In other words, bridge BACnet and LonWorks to Ethernet using TCP/IP and HTTP (Hypertext Transfer Protocol), which is the protocol of the Internet. The result leverages the huge installed base of networks that exist in customer's facilities, eliminating the need for costly, proprietary, and dedicated network solutions. Using Internet connections that are already in place provide greater access to control systems at a lower cost, both initially and over their life-cycle.

For this to happen, the infrastructure must meet certain criteria. It must: 1. Support multiple open control system protocols, such as BACnet, LonWorks, Modbus, etc. 2. Support IT industry standards for networking protocols, information transfer, document formatting, and data access, such as Ethernet, TCP/IP, HTTP, HTML, XML, CORBA, and others. 3. Reduce the total cost of ownership by adopting a thin-client, multiple server architecture where network-centric applications are used, which are platform and operating system independent. 4. Provide security in order to maintain the determinism and integrity required for real-time distributed control. 5. Support legacy protocols, which allows customers to move their existing systems forward cost effectively, thereby protecting their investments and providing a straight forward and affordable migration path to newer open protocols.

A Detailed Look At The Infrastructure

Let's examine this infrastructure in detail and look at the features necessary to achieve this level of openness.

Supports multiple open protocols - To be truly open and flexible, the infrastructure must support multiple open protocols. In addition, to be truly effective, the infrastructure needs to support other methods of data transfer often used for control devices, such as DDE (Dynamic Data Exchange) and OLE for Process Control (OPC). By supporting multiple control or "field side" protocols, the customer's options are not limited. Whether the customer desires more flexibility to support competitive bidding or they simply want to be able to choose the best possible product for a given application, multi-protocol support provides the customer with the ultimate in variety of choice both in terms of product and supplier.

Supports IT industry standards - The Internet uses standard methods for information transfer and document formatting that allow anyone to expose information on the Internet and have that information viewed by someone else. These standard conventions ensure that no matter what browser a person uses, they will be able to access information on the Internet, regardless of its source. TCP/IP, the transport mechanism used to move data on the Internet, and HTTP, the common protocol used to exchange information on the Internet, are the standard communication protocols by which information is exchanged and shared freely on the Internet. Then, there are the HTML (Hypertext Markup Language) and XML (Extensible Markup Language) standards. These define the format in which information is presented in a Web Browser. Using these standards, the Internet has become a powerful and extremely open mechanism for exchanging information and conducting business.

When dealing with other applications in a customer's enterprise, it is not enough to simply move information between users. The infrastructure also needs to be able to exchange information between the control system and other applications in the enterprise. These applications could range from a simple spreadsheet program or database, to an enterprise-wide asset management or accounting and budgeting application. Or, the applications could involve energy modeling and prediction, data visualization, real-time utility pricing and other supply-side management applications. To accomplish this, the infrastructure must be able to support adopted practices in the IT world for this type of data access. Common methods include; relational databases that support Structured Query Language (SQL), Open Database Connectivity (ODBC), and Java Database Connectivity (JDBC).

The infrastructure needs to take full advantage of the technology and standards already in place, namely; Ethernet, TCP/IP, HTTP, HTML, XML, SQL, and others. This brings the same level of openness and standardization to real-time control systems that the Internet provides today in the IT world. Additionally, it eliminates the burden on facility managers and IT administrators of having to deal with managing proprietary protocols as are typical in today's control system client/server architectures. Finally, it lowers the cost of the system by using the networks already in place without having to add additional networking schemes or secondary networks because of potential incompatibilities between an owner's IT network and the control system's network. If the situation warrants it, or the customer desires, the networks (control and information) can be separated. However, in most cases, there is sufficient bandwidth to support both if the infrastructure is a good "network citizen". That is, the infrastructure, to be truly effective in both performance and cost, must use very little network bandwidth. To accomplish this, the infrastructure should utilize server-side applications (servlets), be event-driven, and use lightweight applications or applets that run within a standard Web Browser. This also means that to update real-time values, the infrastructure must be designed to only update individual values (Java objects or applets) on a Browser screen, not the entire page. Re-writing the entire page would take up megabytes of bandwidth for each value change and prevent true real-time updating. The infrastructure must also post these updates upon a value change automatically, not on a fixed time interval, nor by requiring the user to hit a "refresh" or "reload" button to get updates. In addition, the infrastructure must also be able to pass the data through corporate firewalls without a lot of setup hassle, and it must incorporate a communications protocol that passes easily through the firewall but still maintains the security mechanisms that corporate IT groups demand.

Reduce the total cost of ownership - To meet the need to reduce the total cost of ownership and provide for more effective system administration, the client/server architecture is replaced by the thin client/multiple server model. This is exactly how the Internet works today. Multiple servers all over the world, connected via the Internet protocol, using HTTP to move information. Thin clients, or Web Browsers, access these servers without requiring any client-side application to be installed on the user's computer. Java, a programming language developed by Sun Corporation, was written expressly for network-based applications, specifically the Internet. Java provides many features necessary for network-based applications, including security. But, perhaps one of the most significant features is its platform independence. Java, using what's known as a Java Virtual Machine, runs on literally any processor and operating system. This gives the owner the freedom to utilize the computing platforms and operating systems they already have without the need to purchase specific machines just for the control system application. It generally runs on any computer platform: 486, Pentium, Mac, etc., and any operating system: Windows 95/98 or NT, Solaris, Mac, Linux, etc. In other words, there is little or no demand placed on the client machine other than the Web Browser itself.

Considering sites that require access by multiple users, this architecture represents significant savings over traditional client/server architectures because there is no client-side application to purchase and support. The user is not limited to a particular computing platform or operating system and there is nothing taking up disk space on the client machine other than the browser. In the thin client architecture, even system administration is simplified because graphics, for example, are only resident on the server. There is no need to copy graphics to each client machine and ensure that every client has the latest copy of all the graphics required for a user to interact with their system. System upgrades are easier and less expensive because only the server software needs to be updated. There is nothing on the client machines to upgrade in the thin client/multiple server architecture.

The traditional model of having dedicated operators monitoring CRT displays or alarm printers isn't very efficient. With customer's trying to gain additional productivity and efficiency everywhere they can, the infrastructure needs to support their efforts to do so. To help customers address this problem, the infrastructure must offer the ability to email critical information, such as alarms, to alphanumeric pagers, email-capable cell phones, wireless PDA's and similar types of devices, to enable fast response to building conditions without having to sit beside a display or printer. With this support, the facility manager or his designated maintenance personnel can be anywhere, performing other tasks, and still be able to respond instantly to problems anywhere in the customer's facility or group of facilities.

Provide a secure and reliable environment - There is no question that by using the power and openness of the Internet, control system customers enjoy many of the same benefits as do the users of IT applications today. However, when it comes to control, the infrastructure must provide a secure environment that prevents unauthorized access. Having the lights go out due to an unauthorized user command is not something a facility manager wants or should have to deal with!

An infrastructure built on the Java language provides inherent security and protection, including the same protection mechanisms used for credit card transactions over the Internet. In addition, because the infrastructure supports and uses IT industry standards, methods, and practices, common techniques such as personal and corporate firewalls and other network-wide security measures are employed. In other words, since the infrastructure uses standard IT network technologies, the same security, monitoring, and network administration tools can be applied to the control system devices on the network as are used today to protect, manage, and maintain a corporation's computers, printers, network storage devices, and more.

By using a multi-server architecture, as opposed to the typical client/server model, the infrastructure provides a more reliable system architecture. In the client/server model, there is a dependence on a single server for management of data, user interaction with the system, annunciation of alarms, etc. In the single server model, system scalability is limited to the capacity and performance limitations of the single machine. With the multi-server model, there is no dependency on a single machine. Instead, all system functions are distributed across multiple servers to provide greater levels of reliability and performance. What's more, with the multi-server infrastructure, the system becomes completely scalable. There is virtually no limit to the infrastructure's size or performance, because as the system grows more servers can be added.

Support legacy protocols - There is a huge installed base of proprietary control systems. These systems can be at the very beginning of their life cycles, the very end, or anywhere in between. But regardless of their age, they represent a significant investment that the customer has already made. It is important to recognize that this investment must be protected, while at the same time allowing the customer to take advantage of today's open and standard technologies.

In addition, there are many customers who have multiple systems and protocols that they have to maintain. In today's competitive world, this presents an exceedingly heavy burden for the owner, to train operating personnel and maintain their knowledge levels on multiple systems. With mergers, acquisitions and industry consolidation, today's building managers are finding themselves responsible for an increasingly large number of facilities and because of this, a greater number of types of systems they have to operate and maintain.

To be truly effective, the infrastructure must give customers the ability to not only use their existing systems, but, provide a path for migrating and expanding their systems using the newer, open standards and technologies. The infrastructure should allow customers to use their existing proprietary protocols, along with newer, open protocols like BACnet and LON in one seamless system, using a standard Web Browser with a common method for typical operator tasks such as scheduling, alarming, logs, charts and real-time graphic displays, regardless of where the data is coming from, or going to, or what protocol is being used. By providing this performance, a customer can both protect their existing investment and truly achieve the operational cost savings they desire.

In order to deliver integrated solutions economically, the infrastructure should include a common object model to represent all of the various devices, applications, control functions, etc.. The benefits of a common object model to represent the various data structures becomes evident when attempting to tie multiple vendors systems and products together into a cohesive, interoperable system. Having a robust library of Java objects (sometimes referred to as "Java Beans") makes the task of creating applications that work across multiple protocols far easier than trying to use gateways or routers that simply pass data from one network to another or creating database "mapping" of one protocol's data structures to another. The Java objects enable data translation to occur without the user having to understand the underlying protocols of the various interconnected products. Further, the task of linking data to graphics becomes easier due to the Java objects' common set of viewable properties as opposed to having to deal with each manufacturer's unique or proprietary data structures.

Figure 1 - Infrastructure Block Diagram

Figure 2 - Infrastructure Architecture - Single Site 

In this example, the core of the infrastructure is a platform that combines the functions of an integrator, a real-time control engine and a server. Multiple platforms may be connected locally via a LAN. An unlimited number of users can access these servers using a standard Web Browser, regardless of the operating system or type of PC/Workstation being used. Data can be passed between the platforms for global control, monitoring and accessing data from anywhere in the system.

Figure 3 - Infrastructure Architecture - Multiple Site 

In this example, each site may have one or more platforms. Multiple platforms may be connected locally via a LAN and the sites themselves can be connected via a WAN or the Internet. An unlimited number of users can access these servers using a standard Web Browser, regardless of the operating system or type of PC/Workstation being used. Users can access data anywhere in the overall network and data can be passed between platforms anywhere in the overall network.

Conclusion

The Internet has had a profound effect on almost everything we do. Modern control systems now have the ability to take advantage of the power of the Internet and the economies of scale provided by ubiquitous IT technologies and standards such as Ethernet, TCP/IP, HTTP, and XML, to name a few. Bringing together open communications protocols for control devices and these IT technologies, provides customers with options and functionality at cost levels that were never before possible. A truly open, infrastructure that supports real-time control systems as well as the enterprise applications and information flow, is more than just putting some data in a Web Browser, it is the enabler for an unlimited number of solutions for any size or type of facility.

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