PID control

Abstract

The use of Proportional-Integral-Derivative (PID) controllers for integrating processes with dead time is discussed in this chapter. Since PID controllers are the most adopted controllers in industry and there are many different design methods, only those techniques specialised for IPDT processes are discussed in this chapter. After having introduced PID controllers, identification methods suitable to be applied in an industrial context are presented. Both open-loop and (relay-feedback-based) closed-loop techniques are considered. Then, tuning methods are explained. Without aiming at presenting all the tuning methods proposed in the literature, different approaches are highlighted with the purpose of showing how the problem can be tackled from different points of view. After having presented empirical tuning rules, analytical design techniques are explained, in particular those based on the Internal Model Control. Then, frequency domain approaches are discussed. Subsequently, techniques based on optimisation criteria are presented, in particular those based on the optimisation of integral criteria and on H ∞ loop shaping. Note that the classification done hereafter is subjective because, actually, there might be overlap between the different methods considered (for example, the Internal Model Control strategy is analytical, but, at the same time, it minimises integral criteria).