02 March 2001
Remote wireless presence in field device management
by Harri Cederlöf, Jouni Pyötsiä
Wireless access protocol and small screen formatting keys to handheld plant monitoring.
In smart field device management and condition monitoring, there are two crucial challenges: information compression to knowledge and easy access to this valuable knowledge.
Today, smart field devices collect huge amounts of information about device performance and operation. This information flow increases the complexity and workload of operators and maintenance people.
The challenge is to create a system that automatically processes this information flow to online knowledge. Further, remote online access to this valuable knowledge is needed.
Diagnose the field gadget
The ultimate goal of process automation is to increase the yield, decrease the total costs of ownership, and improve the safety. In new process automation architecture, based on fieldbus communication, smart field devices have great potential for meeting these requirements.
The importance of field device diagnostics will increase in the future. During a field device's lifetime, much new information will become available and accessible. In this situation there is a danger that the information flow coming from the smart field devices will increase rather than simplify the complexity and workload of operators and maintenance people.
Therefore, managing this information flow is the key to maximizing safety, performance, and profit. In information management and condition monitoring of smart field devices, there are two crucial challenges: information flow compression to online knowledge and easy online access to this valuable knowledge.
Further, there is a need to speed up the knowledge creation or learning, utilizing the Internet/intranet communication network. Fortunately, the emerging software agent and latest cellular communication technologies provide new opportunities for meeting these challenging requirements.
Expert systems assay health
A field agent is a software component that follows the health of field devices. It is autonomous, it communicates with its environment and other field agents, and it learns new things and delivers new information to other field agents. The use of the field agent is invisible to the user. It delivers reports and alarms to the user by means of existing and well-known technologies such as an intranet and e-mail.
The expert system determines the health of the devices with the help of two indices: a control performance field agent index and a maintenance need index. The control performance index is key in evaluating the operation of control valves relating to the control performance of the whole control loop. The maintenance index is key in predicting existing and future needs for maintenance.
The learning of the field agents occurs via the field agent server. The field agent server could be a global server that receives new information from field agents all over the world by e-mail, interprets the new information, and, if it is useful, sends it to other field agents to update their knowledge.
The field agent server centralizes information gathering. It also maintains the information on performance and maintenance from different plants. This information is valuable for life cycle management and selecting optimal solutions for similar applications.
Handheld has limitations
Most Internet technology is for desktop and larger computers with high bandwidth and generally reliable data networks. Mass-market handheld wireless devices present a more constrained computing environment, compared with desktop computers.
The limitations of handheld devices include less powerful CPUs, less memory, restricted power consumption, and smaller displays. Similarly, wireless data networks have a more constrained communication environment than wired networks, causing limitations in the form of less bandwidth, less connection stability, and less predictable availability.
These limitations present a need for technology specially designed for connecting wireless data and the Internet. At present, the most promising method for providing a standard mobile terminal with Internet capability is via wireless application protocol (WAP), as defined by the Wireless Application Protocol Forum.
WAP specifies an application framework and network protocols for wireless devices, such as mobile telephones, pagers, and personal digital assistants.
In order to accommodate wireless access to the information space offered by the World Wide Web, WAP uses well-known Internet technology. It meets the constraints of a wireless environment. Because of the constraints mentioned above, services created using hypertext markup language (HTML) would not fit well on small handheld devices.
Developing a markup language—wireless markup language (WML)—adapted to these constraints was important. WML offers a navigation model designed for devices with small display and limited input facilities. In order to save valuable bandwidth in the wireless network, WML uses a compact binary code format.
WAP also provides a scripting language, WMLScript, for supporting more advanced tasks, comparable to those solved by using, for example, JavaScript in HTML.
Present to mobile user
The new solution for wireless presence in field device management is providing mobile connection to the information generated by the field agent. WAP technology makes the connection.
The system consists of three PC servers connected to the factory intranet. The field agent monitors the devices and collects device information and diagnostics data into the database located in the server. The mobile terminal makes a wireless data connection to a modem connected to the WAP gateway PC running NT Remote Access Service.
The WAP gateway receives queries from the phone, decodes them, and delivers them to the Web server. Java servlets running on the Web server receive the inquiries and generate a WML deck containing the information that the mobile terminal user requested from the database.
The WML deck transmits to the WAP gateway, which encodes the data to binary format and sends it to the wireless terminal.
Because of the limited display properties of mobile terminals, information presentation requires much attention. Only the most important information should load for the mobile user. This information includes simple status and the analysis history of the devices.
Offers advantages beyond
Field device performance has a strong influence on process performance and reliable operation in more distributed process automation architecture based on fieldbus communication.
In this situation, easy online access to the knowledge that describes field device performance and maintenance needs is crucial. This decreases the complexity and uncertainty in decision making and reduces the workload of operators and maintenance people.
The upcoming software agent and cellular communication technologies give new alternatives and solutions in field device management. The latest cellular communication technology based on WAP provides wireless online access to the valuable knowledge.
Depending on the capabilities of the mobile terminal, even high detail graphics can display to the user. Together with a powerful online condition monitoring system based on the smart agents concept, we can ensure performance that offers advantages beyond those of existing systems and solutions. IT
Figures and Graphics
Sidebars
Author Information
Harri Cederlöf works for Metso Automation (formerly Neles Automation), www.metso.com. He is a senior software specialist in the technology unit.
Jouni Pyötsiä works for Metso Automation (formerly Neles Automation), www.metso.com. He is the vice president of the technology unit.
Read questions answered by our experts or join the email list.
