IMC Tuning Method

This results in slight differences between the resulting tuning formulae. Table 3.6 lists the formula commonly required, but many versions will be found in the literature. 

It is possible to use the technique to quantify other parameters in the control algorithm. For example Rice and Cooper (Reference 11) developed formula for a - the term used in derivative hltering so that, on those DCS which permit the engineer to change this value, it can also be optimised. 

Of course it is possible from this chart to construct another allowing the engineer to choose a value for X to give the required MV overshoot. Indeed this has been done and the 

from this chart, simple formulae could be developed. For example for a 15 % MV overshoot. 

However for this approach to be adopted, such charts and formulae would have to be developed for every version of the PID algorithm, for every variation of the tuning formulae. 

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IMC (internal model control) replaces the PID controller completely. Its name derives from the fact that it can be shown that it is effectively the same approach as tuning a PID controller using the IMC tuning method. However, this is only exactly true if there is no deadtime. With deadtime IMC will outperform IMC tuning in a PID controller. 

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