Verification of robust properties of digital control closed-loop systems

Abstract

Robustness is specific property of closed-loop systems when the designed controller guarantees control not only for one nominal controlled system but also for all predefined class of systems (perturbed models). The robust theory is mainly exploited for design of the continuous-time systems. This paper deals with an experimental simulation investigation of robust properties of digital control closed-loop systems. Minimization of the Linear Quadratic (LQ) criterion was used for the design of control algorithm. Polynomial approach is based on the structure of the controller with two degrees of freedom (2DOF). Four types of process models (stable, non-minimum phase, unstable and integrating) were used for controller design. The Nyquist plot based characteristics of the open-loop transfer function (gain margin, phase margin and modulus margin) served as robustness indicators. The influence of change of process gain was chosen as a parametric uncertainty. The experimental results demonstrated that a robustness of examined digital control closed-loop systems could be improved by addition of user-defined poles (UDP). © ECMS Zita Zoltay Paprika, Péter Horák, Kata Váradi,Péter Tamás Zwierczyk, Ágnes Vidovics-Dancs, János Péter Rádics (Editors).