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Pneumatics learn to think

Pneumatics learn to think

As Group Technical Director, Chris Bramley's focus is the coordination of product design, development, and engineering resources worldwide, with the aim of introducing new products across the entire pneumatics spectrum. He is also responsible for the implementation of emerging technologies such as the integration of electronics into pneumatic devices. Part of the Norgren team since 1987, Bramley has worked in a variety of development roles with particular emphasis on product technology. His previous research and development experience was gained in the automotive, offshore, and aerospace industries.

Bramley explains how the integration of electronics into pneumatic devices is bringing built-in fault diagnosis and intelligent systems ever closer.

Design News: Is diagnostic capability coming to pneumatics?

Bramley: Computers put a message on the screen to tell us when the printer is out of paper. Copiers tell us where to look for the paper jam. And even a washing machine knows that the water supply is defective. The necessary technology for diagnostics is all around us, so why don't we see it in pneumatics? Probably because, until recently, everybody regarded pneumatic products as dumb components to be built into a system designed by someone else. But the integration of electronics into pneumatic devices is changing all the rules.

Q: Why has this change taken so long?

A: The general adoption of relay control for industrial processes in the post war boom led to the use of solenoid valves as the interface between the "logic" and the pneumatic control valve. Diagnosis and fault correction was limited to the exclusive fraternity who had been trained in the mystic arts of "ladder logic charts." Relays were eventually replaced by electronic devices-initially simple sequencers, and subsequently the programmable logic controller (PLC). Although these devices were essentially small computers, they were designed to be programmed in "ladder logic" so that they would resemble existing control philosophy. This created two problems: It limited the inherent flexibility of the controller by superimposing the restraints of ladder logic, and it maintained the power of the "fraternity" who were opposed to anything which would undermine their position. This in turn supported the idea that the world is divided into inputs and outputs that are discrete and handled separately.

Q: How has the growing adoption of Fieldbus protocols affected the issue of built-in pneumatic diagnostics?

A: Generally, the rationale for using Fieldbus for control of pneumatics is to simplify the wiring design, thus saving on installation costs and reducing commissioning times. The choice of Fieldbus and the benefits achieved are all under the control of the OEM or end user, and not the pneumatic manufacturer. Any diagnostic functions must therefore be implemented in the main controller from information passing over the bus. Unfortunately, since the pneumatic valve is still regarded as a simple output device, it cannot provide much of the data needed to create the diagnostics. Even if it did, the resultant communication load on the bus and the processing in the main controller would probably preclude its use, especially in high-speed applications. The move to Fieldbus has also resulted in the responsibility for specification moving to the system design engineers, away from tra- ditional mechanical engineers with an understanding of pneumatics. The pneumatic control will, in the future, be regarded as another block of output and its internal function will not be understood. The need for some form of built-in fault diagnosis has never been higher.

Q: What is the solution?

A: The key to effective diagnostics lies in having some processing power built into the product. The printer, the copier, and the washing machine all need a controller to function, and this controller stores the data and carries out the analysis needed for the diagnosis of problems. The latest valve island products from Norgren and other leading pneumatics companies now incorporate electronics within the valve assembly. This is either as a one-piece PCB to connect all valves, or as a chip on each valve station to allow simple flexible connection of valves, input and output units. The use of an internal "bus" reduces the amount of wiring in the island and allows more units to be connected together. Once products are introduced with on-board processing, simple diagnostics can be achieved with little additional cost.

Q: Where will this diagnostic capability eventually lead?

A: So far, we have looked at the ability to check status and to provide warnings when failure has occurred. This capability will ease troubleshooting and speed up the task of replacement after a device has failed. But what if we could predict a problem before it happened? By monitoring the change of various parameters, it will become possible to predict the malfunction of a valve or cylinder before it occurs. Then the unit can be changed during a routine maintenance period, and no costly unscheduled plant stoppages will happen. The intelligence to do this is already here.

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