Patent ID: 7035695

Claim:
A method of tuning a controller for a process in a feedback control system comprising the steps of: (a) bringing the system into asymmetric self-excited oscillations via the introduction into the system an element having a nonlinear characteristic in series with the process, and applying a constant set point signal f 0 to the system, so that the error signal is the difference between the set point and the process output signal, the error signal is an input of the nonlinear element, and the output of the nonlinear element is a control signal for the process; (b) measuring the frequency of the oscillations Ω, the average value of the process output signal y 0 , and the average control signal u 0 , and wherein the averages are taken over the period of the oscillations; (c) choosing the process model, parameters of which have unknown values; (d) identifying of the parameters of the process model with the measurements obtained; (e) tuning the controller in dependence on the identified parameters of the process model, wherein the original process model with unknown parameters is transformed into the form of a formula of the locus of a perturbed relay system (LPRS) being a complex function, which has same unknown parameters.