Automatic tuning of commercial PID controllers

Several methods have previously been developed that automatically tune PID controllers. The PID algorithm itself is usually essentially simple, but commercial implementations of PID controllers contain a multitude of additional features which embody the experience of many years of application. It is therefore prudent to retain those features when introducing self-tuning; basically sound self-tuning methods have failed because these vital details have not been attended to. To take account of these points, the approach taken in this chapter is to use a standard commercial PID controller (a Eurotherm 820) and use a continuous-time self-tuning PID controller to generate its parameters as opposed to using the self-tuning PID controller to generate a control signal. The self-tuning PID controller is implemented on an Atari PC and communicates via an RS-232 port using the Eurotherm communications protocol.