H∞ Proportional-Integral Control of a Turbofan Engine

Abstract

This paper presents the design of a thrust controller for a single-shaft turbofan engine at the operation point defined with following parameters: altitude = 0, Mach number = 0, angle of attack = 0. In that case, the dynamics of the engine depends only of the shaft angular velocity. Mathematical model for controller synthesis is obtained by solution of the set of nonlinear equations. Due to complexity of the engine, parameter uncertainties and exposure to various disturbances during exploitation, the H∞ methodology for controller synthesis is applied. Since H∞ based controller presents linear controller, it requires linear model of the plant for synthesis. Due to that, the plant needs to be linearized. From nonlinear simulation, the 1st order transfer functions can be obtained for selected intervals of shaft angular velocities. For controller synthesis, the fuel supply system is also included as the 1st order transfer function. Since obtained controllers present higher order controllers which may not be feasible for a real-time implementation because of hardware limitations, they are reduced to proportional-integral (PI) controllers by using the balanced reduction. Obtained controllers are then combined via gain-scheduling approach and simulation is performed.