Report shows slow take-up of RF real-time control

A large percentage of those using wireless technology in industrial applications are applying it to control applications, or both control and monitoring.

RF/microwave wireless products are being used more in industrial control applications, but exactly how?.

According to a recent study by Venture Development Corporation (VDC), a large%age of those using wireless technology in industrial applications are applying it to control applications, or both control and monitoring.

However, further analysis reveals that the identified control applications are largely in setup and maintenance and that reliability concerns are inhibiting adoption for operational real-time use.

VDC asked users to identify the specific application in which wireless products are being used.

Datacommunications, controller programming and controller maintenance were the three most identified, both currently and planned.

This indicates wireless use in machine and process setup and troubleshooting is far more common than for operational real-time control.

On the other hand, users also identified wireless control of cranes and hoists.

This is in fact a well-established industrial market for wireless operational real-time control, where the technology has been used for over 25 years.

Here an operator controls the crane or hoist through a remote wireless terminal, either fixed or portable (such as handheld or belly box types).

Although this is "operational real-time" control, it is not fully automatic control, as the operator is an integral part of the control loop.

True real-time automated control poses a much greater concern to implementers than the monitoring of control applications.

The two most identified problems encountered by users in both RF/microwave wireless industrial monitoring and control are signal reception dropouts/blockage and RF interference.

With these concerns, users remain reluctant to embrace wireless technology for operational real-time control, where even a slight delay in, or corruption of, data communication could have costly results.

Thus at present, industrial wireless operational real-time control is most commonly found in applications with slowly changing variables, such as temperature control, flow control etc of some slowly fluctuating processes, or in those where the control is via man-made decisions (such as for cranes and hoists), rather than in automated systems where high-speed machinery is being controlled.

Slow process applications are more easily monitored by independent means and independent corrective action undertaken before damage is done if faulty operation is detected (ie there is time for a valve to be manually opened or closed etc).

Likewise, when an operator is actively in control visually, the most obvious safeguard is for shutdown of the operation if faults are detected.

Controlling slow processes also requires less bandwidth, as datarate requirements are lower.

Thus, many of the existing industrial operational real-time control applications using wireless technologies operate in the available RF spectrum bands in the 400, 800 and 900MHz bands where there is adequate channel bandwidth for these applications.

However, higher speed applications can require more bandwidth, which in turn may necessitate operating in higher microwave frequency bands such as 2.4 or 5GHz.

In general, moving to higher frequency bands makes the problem of signal dropouts and/or blockage worse.

With regards to whether interference is better or worse, this depends on the local environment where the system will operate.

Another major reason for wireless usage is to reduce wiring costs, and these savings tend to be greater for large distributed systems.

These tend to be slow process-type applications, rather than involving high-speed machinery.

Thus, there may be little savings in wiring costs for many discrete manufacturing operations, and use of wireless technology for operational real-time control may not be attractive.

Furthermore, these may require operating in higher RF/microwave frequency bands in order to have adequate bandwidth, and typically as the frequency goes up, so does the cost of the RF/microwave components.

However, wireless technology may still be attractive for use by personnel with portable operator interface terminals for machine setup and troubleshooting.

As both users and vendors of wireless products gain experience in industrial monitoring and control applications, the capabilities and limitations of these will become more apparent.

It appears that the most near-term potential for operational real-time usage will be for slow-moving process industry applications, where data transmission faults would not pose a serious risk.

VDC analyst Jake Millette points out for these that "Wireless operational real-time control holds many potential advantages over wired solutions", but he also states, "even here small steps must be taken as mistakes can be expensive".

It is expected that use of RF/microwave wireless technology in operational real-time control will eventually extend into other applications, in both discrete and process manufacturing.

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