title: PID controllers' fragility.
abstract: In this paper, an index for measuring fragility of proportional integral derivative (PID) controllers is proposed. This index relates the losses of robustness of the control loop when controller parameters change, to the nominal robustness of the control loop. Furthermore, it defines when a PID controller is fragile, nonfragile or resilient.
authors.affiliation: Departamento de Automática, Escuela de Ingeniería Eléctrica, Universidad de Costa Rica, PO Box 2-10, 2060 UCR, San José, Costa Rica. valfaro@eie.ucr.ac.cr
authors.forename: Víctor M
authors.initials: VM
authors.lastname: Alfaro