Fluidics

The technology of using the energy of moving gases or liquids to perform sensing, logic and control functions is being used more and more in diverse industries. Fluid power has, of course, been used for many years, but it is only in the last decade that engineers realised that fluids can be self-controlling and, moreover without moving parts.

The fact that fluid circuits could be manipulated in much the same way as electrical circuits stimulated research and developed in many countries. The basis of much of the work derives from properties of ‘pure fluid' devices i.e. those that do not use moving parts. There are many useful devices which use moving parts, but the essence of fluidics can best be appreciated by considering the ‘pure-fluid' types.

These can best be likened to electronic valves or transistors and typical devices are bistables and OR NORs. The are often referred to as ‘fluid amplifiers' because they can operate as conventional amplifiers and provide the functions of amplification, switching, memory etc. The basic fluid elements included in the Plessey Experimental Kit are ‘pure-fluid' types. In particular are operated digitally, making them ideal for digital control applications. Design principles are based on the ‘wall-attachment' effect ( often referred to as the ‘Coanda effect'‘ after the Rumanian Henri Coanda who discovered the principle), in which the tendency of a moving gas stream to latch itself to a nearby wall, or face, is utilised. Full descriptions of the basic Plessey elements can be found in the associated literature and articles in the brochure included in the kit.

Fluidic devices may be ‘digital' or ‘analogue' in operation. The former operate in an ‘ON OFF' mode, the latter in a proportional mode with outputs varying in proportion to the control signals.

The fluidic devices in this kit are, primarily, digital in operation. From the logical design viewpoint a digital fluidic device equates with, for example, an electronic relay who contact may be either open or closed; or a transistor which is either conducting or not conducting.

Fluidic system design closely follows the same logical steps as those associated with the design of electrical or electronic systems.

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