Published online by Cambridge University Press: 04 July 2016
Every control system employs some computing elements and it is customary to designate systems after the type of computing predominantly used in them. Thus, we have hydromechanical systems, pneumatic systems, fluidic systems, analogue electric systems, and so on. Traditionally, as described by Watson, the aircraft gas turbine has used hydromechanical control (see Fig. 1). The diagram does not depict any particular engine component but illustrates some of the principles used in a variety of present-day systems. A mixture of bellows, springs, cams, orifices, etc, compute according to their particular arrangement; frequently the fuel itself is used as the computing medium. Essentially such systems compute continuously using physical representations of the measured parameters. They are, therefore, of analogue form.