Robustness in PID control

© Springer-Verlag London Limited 2012. Robustness should not be taken for granted. After decades of gaining acceptance, Robust Control Theory has permeated practically every approach to controller design. Of course, PID cannot be an exception. The introduction of robustness considerations within the PID paradigm has created an active focus of research. During the last decades, a number of approaches have emerged introducing new considerations into the design of PID controllers by considering the robustness as a design specification. Of course, this can take several forms and formulations. This chapter specially concentrates on those approaches that lead to robust tuning rules. The use of different robustness measures is presented, and the importance of ensuring the specifications are met. This fact allows for a posterior analysis of the well-known (but not quantitatively analyzed) Robustness/Performance tradeoff. A possible route to this analysis is presented at the end of the chapter as a suggestion on how to approach this problem and have a clearer idea of the price paid for increasing the demand for robustness.