The key to achieving good control over any process is to have a good understanding of its dynamic ( time- varying) behaviour. Increasingly, this means actually building a mathematical model of the process and using it either to test potential control schemes, or even using it directly in the construction of the controller itself.
In concept, dynamic modelling is relatively simple. The only equation the modeller has to remember is the continuity equation:
Rate of Accumulation = Rate in - Rate out + Rate of Generation
Remembering this equation, and getting some practice in applying it to different situations will get you a long way towards becoming a competent dynamic modeller.
This section discusses some aspects of dynamic modelling : building the initial modelling equations; solving them using computer and analytical techniques; and predicting the expected types of behaviour from a knowledge of the model equations.