Dear Lagos, thank you for the question.

The answer is not immediate because it depends on the environment and type of application.

There are a lot of available technologies and their use for automation depends on the application requirements.
For example, mobile robotic applications that have visual feedback predominantly use Wi-Fi because they need a high bandwidth for real-time video transfers. However, for transmitting the data of the robot sensors and alarms the demands in bandwidth are much lesser but the reliability must be higher and Bluetooth or ZigBee could be preferable for this traffic.
Moreover, the same system may present requirements of different classes and require different type of networks to fulfill its requirements. For instance, let us suppose that some separated units compose a motor motion controller. The units are embedded in the sensors and actuators of the motor that it controls. Suppose that these parts are wirelessly interconnected. Such a physically distributed motion controller, if wirelessly distributed among the parts of a motor, has different requirements when performing the position control loop (30 Hz for instance), the velocity control loop (2 kHz for instance) and the current control loop (10 kHz for instance).

So, different technologies will have to coexist in the manufaturing environment.

Generally speaking I would say that ZigBee is a good candidate for sensor networks, Bluetooth and Wi-Fi (in PDAs for instance) are good candidates for local monitoring and supervision and GPRS or UMTS are good candidates for supervision of remote units. For motion control it is yet to soon to state the choice because one of the promising technologies (UWB) is still under development.

Hope I answered to your question,
Cheers
Carlos Cardeira

Wireless USB is based in UWB and the applications in manufacturing are promising because of:

1. high speed,
2. higher resistance interference
3. coexistence with other networks
4. low power

However this is not pacific and some authors just polemically argue that it would just be better to skip this UWB subject on fears of the very large band required by this technology. The defenders of the technology claim that even if we have 30 UWB devices in a 6 feet radius that would not interfere with the reception low power signals like for instance GPS signals. GPS transmissions are out of the UWB band, but were cited here just for a comparision of the power levels.

However there are some other problems to solve:

1. There isn’t a stable standard. The IEEE committee voted to disband because it was unable to chose among the competing proposals.

2. In Europe the use for UWB remains forbidden because the FCC regulations that authorized the use the ~3to~10 GHz band for public domain (regarding that the emission power is lower than –41.3 dBm/Mhz), were not transposed to Europe.

As for ABB WISA, I would suggest contacting Ulrich Topp or Dirk John from ABB Corporate Research (Germany) who made a recent presentation in the WFCS 2006, the 6th IEEE International Workshop on Factory Communication Systems that took place last week in Torino.

Best regards,
Carlos

Hello,
I think WISA is defintely the way to go as far as expansion of the wioreless network to the whole factory and immunity against EMI are concerned. Having said that, wireless USB could also be an option, as long as EMI issues and data protocol conversion are throughly taken care of.

Robert