The PID controller is widely used, and several methods have been proposed for choosing
the controller parameters to achieve good performance. The controller tuning problem is set
up as a semi-infinite program (SIP), with the integrated squared error (ISE) or the H∞ norm
of the frequency domain error function (| E (s)|∞) as the objective function, and H∞
constraints for robustness and noise attenuation. Previous authors considered discrete
points to enforce the H∞ constraints, however this is an outer approximation that does not …