When is PID a good choice?

A new and freely available model-based PID design tool for Matlab is introduced. It can be used to solve Maximal Integral Gain Optimization (MIGO) and (load) Integral Absolute Error (IAE) problems. Robustness is ensured through H-inf constraints on the closed-loop transfer functions. A Youla parameter (Q design) method for comparison with the optimal linear time-invariant (LTI) controller for the considered IAE optimization problem is presented. Several realistic design examples are provided, in which the tool is used to compare achievable PID and optimal LTI controller performance, to illustrate whether PID is a good choice for a given combination of process dynamics and closed-loop robustness requirements.