Applying WAP Technology in Control Applications

Author(s):
Pee Suat Hoon - Singapore Polytechnic School of Electrical And Electronic Engineering

Industry:
Telecommunications

Products:
Lookout, FOUNDATION Fieldbus

The Challenge:
Controlling and monitoring a process remotely using WAP technology.

The Solution:
Using National Instruments Lookout and Fieldbus configuration software to have constant access to the plant info from a remote site.

Standardizing the Way Mobile Phones Access Information and Services
Wireless application protocol (WAP) is an open specification that attempts to standardize the way mobile telephones access information and services. It is an information enabler because it provides a method to obtain simple content from the Internet to portable devices. We base the protocols on existing Internet standards, including HTTP, and we optimise them for constraints of wireless environment.

Pee Suat Hoon at Singapore Polytechnic experimented to control and monitor a Foundation Fieldbus pilot plant with a WAP hand-held device using National Instruments Lookout and Fieldbus configuration software.

The WAP protocol uses a layered architecture similar to that of a computer network. While the lower layers are not particularly interesting to Web programmers, the top layer, which is the application layer, specifies the use of wireless markup language (WML) and WMLScript, collectively known as the wireless application environment (WAE). They are required for coding the application. WML optimises small screens for easy navigation without a keyboard, while WML Script is the counterpart of Javascript for WAP telephones.

Implementing WAP in Control Applications
We also can use a WAP emulator if the WAP enabled phone is not available. This is possible by using a Web server to host the WAP services. Because the server must notify the WML browser that it is about to receive a WML page, the MIME types for WML and WML Script must add to the server for different devices to interpret and display WAP content properly.
We can use ASP pages, located at the server directory, for generating dynamic WAP pages, so users can monitor process values and manipulate set points. We used a Microsoft Access database for storing the process variables and transaction records.

We loaded an application server running National Instruments Fieldbus configurator and Lookout for connecting to a Foundation Fieldbus pilot plant. We plugged an NI Fieldbus board into this computer for communicating fieldbus signals to the fieldbus pilot plant.
We executed the following transactions to process a WAP request :
1 A user initiates the transaction by submitting a request to the Web server from the WAP hand-held device. The user does this by clicking a hyperlink or entering an URL at the WAP device.
2 The Web server receives the request, notes that the requested Web page has an .asp filename extension, and starts the Active Server Pages script processor.
3 The ASP script processor reads through the requested page and executes any server-side script code it finds within.
4 The server-side script code loads (creates instances or initiates) various ADO objects. The script code then uses methods exposed by these objects (i.e. it invokes software commands) to access any data sources available on the server.
5 ODBC is one such data source that ADO accesses most. The ODBC data source provides ways to open databases and tables, process SQL commands, and execute other tasks.
6 Eventually, ADO – working directly on its own or indirectly through a data source – sends commands to a data provider. The data provider can be a DBMS, such as Microsoft SQL server or Microsoft Access.
7 The WAP client obtains update of the process variables based on values available from the Access database. At the same time, the Access database is also linked to the Lookout program where process variables are communicated to and from the Foundation Fieldbus pilot plant. Thus, the Lookout program updates the Access database with process variables obtained from the pilot plant, and it transmits set point changes from the Access database to the pilot plant.


Conclusion
According to a recent ARCpoint audio update “HMI and Thin Client = View from Anywhere,” we classified three categories of HMI as the local Web, remote Web, and wireless Web HMI. Wireless HMI is an area that generates a lot of interest because it provides the maintenance engineer the benefit of “view from anywhere” and continuous access to the process.

Because our solution described used the existing infrastructure, it was unnecessary to purchase additional or new HMI software for wireless usage. Therefore, this solution provided a good alternative to other solutions that used special client software by eliminating additional costs. This solution used of existing standard software such as the Web server, and ASP pages that do not require additional efforts to learn.

Besides cost savings, existing system running Lookout and Fieldbus configurator can remain intact, so engineers who had been using Lookout do not need to adapt to a new way of managing the process after implementing this WAP solution.

For more information, contact:
Pee Suat Hoon
Singapore Polytechnic
School of Electrical And Electronic Engineering
Tel: 65 6772 1453
E-Mail:peesch@sp.edu.sg

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