ABSTRACT
This chapter exposes first the inherent control design trade-off of a control system. The presentation is quite self-contained with the purpose of providing a compact perspective of the proportional, integral, and derivative (PID) design problem within the weighted sensitivity problem but without explicit reference and distractions that may arise because of more formal and technical appreciations. Although many changes and innovations have been introduced since its early development during the 1930s and ’40s, the basic idea behind the PID controller still applies successfully in practice. Moreover, in spite of other promising proposals, such as the fuzzy or MPC paradigms, it seems that PID control is here to stay as the preferred control algorithm, at least at the bottom layer. In general, the tuning of the controller must be done taking into account different objectives, such as output performance, robustness, input usage, and noise sensitivity.
