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There are multiple emerging wireless network standards and systems with a menagerie of new names to learn, such as Wi-Fi, Bluetooth, ZigBee, WiMax, and WiMedia. While it will be some time before the markets determine the winning systems, there appears to be three wireless standards that will be used for control and automation, Wi-Fi, WiMax, and ZigBee.

03/01/2005


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There are multiple emerging wireless network standards and systems with a menagerie of new names to learn, such as Wi-Fi, Bluetooth, ZigBee, WiMax, and WiMedia. While it will be some time before the markets determine the winning systems, there appears to be three wireless standards that will be used for control and automation, Wi-Fi, WiMax, and ZigBee.

Wi-Fi (IEEE 802.11b) is short for 'wireless fidelity' and is the trade name promoted by the Wireless Ethernet Compatibility Alliance (WECA). 'Wi-Fi' is used in place of 802.11b in the same way that 'Ethernet' is used in place of IEEE 802.3. Wi-Fi's main advantages in control and automation systems are mobility and reductions in wiring. In many control systems, less than half the startup time is in setting up the hardware—a lot of time is spent in getting the controls 'right' and making sure the control system network and infrastructure are correct. The startup bottleneck is often the control system checkout, with cabling problems a large part of the effort due to the number of lines that need to be pulled and checked. Ethernet and sensor networks have reduced the number of cables, but Wi-Fi connections will reduce cabling and wiring checkout even more.

WiMax (IEEE 802.16a) is a high power wireless broadband system supported by the WiMax forum ( www.wimaxforum.org ). It was developed for long distance runs, up to 25 miles, and replaces cable in truck-line or other high-bandwidth long cable runs. WiMax systems reduce the cost of connections within and between buildings. WiMax can provide automation and control network backbones that are physically separate from business network backbones, significantly reducing security, reliability, and performance issues.

ZigBee (IEEE 802.15.4) is a very low power, limited range wireless system, supported by the ZigBee Alliance ( www.zigbee.org ). ZigBee is unique in that it defines a network mesh where multiple paths exist between nodes, and each node can store and forward information to other nodes. The name ZigBee comes from the zig-zag path of bees that form mesh networks between flowers. Mesh networks provide redundancy and resiliency. ZigBee is designed for very low power drain and can be used in battery-based systems. Initial markets are industrial control, building automation, and home control, with a focus on sensor arrays and digital controls.

One major impact of the new wireless options on manufacturing IT will be increased demands for manufacturing flexibility. Some leading manufacturing companies are already designing and using modular systems that can be quickly reconfigured for different products and production flow layout. Reports on movable equipment and modular construction have been a regular feature at the World Batch Forum ( www.wbf.org ) conferences. The use of wireless networks will accelerate the use of reconfigurable systems by making reconfiguration and checkout even easier. This will increase the demand for flexible control systems, with reconfigurations done in hours instead of days. The wireless networks will allow rapid hardware reconfiguration, meaning that control and automation systems will have to become equally flexible. This will require modularization in control system architecture, design, and implementation.

Control system designers will have to embrace modular architectures and designs, such as those defined in the ISA 88 standards. Recent work by the ISA SP88 committee and OMAC ( www.omac.org ) show how this can be done. Hand-crafted control systems with every part custom-made will need to be replaced with systems assembled from predefined elements, with minimal 'glue' code used to tie them together.

Advances in wireless technologies will have the unexpected consequence of demand for more flexible control systems. Ability to quickly physically reconfigure production lines must be matched with the ability to quickly define and implement new control strategies and manufacturing rules.

Further reading

A good reference work in this area is the electronic book, Wireless Networks for Industrial Automation by Dick Caro, available from ISA ( www.isa.org ).


Author Information

Dennis Brandl, dbrandl@brlconsulting.com , is the president of BR&L Consulting, a consulting firm focusing on manufacturing IT solutions, based in Cary, N.C.




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