A Multi-loop Switching Controller for Aircraft Gas Turbine Engine with Stability Proof

Abstract

In this paper, a Min-Max switching controller containing multiple state feedback regulators and fuel flow rate saturation is designed for a high bypass two-spool turbofan engine. Due to the switching nature of Min-Max algorithm and the presence of saturation function, stability analysis is an important issue in the process of controller design. Therefore, a methodology is presented to analyze the stability of the closed loop system. For this objective, the Min and Max selectors and the saturation block are replaced by their nonlinear equivalents and the structure of the control system is transformed into the canonical configuration of Lure’s system. Then, the condition for absolute stability is extracted using the Multivariable Circle Criterion. An asymptotic stability proof is achieved for the closed loop system and the performance of the designed multiregulator Min-Max controller in tracking a desired fan speed scenario and limit management is compared with the well-known Min-Max/SMC technique.