Tuning PID controllers for a class of unstable dead time processes based on stability margins specifications

The control of unstable second order plus dead-time (USOPDT) processes systems using generalized PID type controllers is investigated in this paper. New tuning rules based on the exact satisfaction of gain and phase margin specifications are proposed. The tuning rules are given in the form of iterative algorithms, as well as in the form of accurate analytic approximations, particularly useful for online tuning applications. The proposed tuning rules are applied for the control of a gravity-biased one degree of freedom magnetic levitation experimental system with very satisfactory results.