A successful method for tuning single-loop PID controllers is the ultimate-point method. This method is based on the identification of the ultimate point of the process’ frequency response followed by its shifting, through appropriate choices of the controller’s parameters, to a specified location of the complex plane. This paper presents an extension of the ultimate-point method to the tuning of decentralized controllers for multivariable processes.
IEEE transactions on control systems technology. Piscataway. Vol. 17, no. 6 (Nov. 2009), p. 1270-1281