Turbofan engine control design using robust multivariable control technologies

A unified robust multivariable approach to propulsion control design has recently been developed at National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC). The critical elements of this unified approach are 1) a robust H-infinity control synthesis formulation; 2) a simplified controller scheduling scheme; and 3) a new approach to the synthesis of integrator windup protection gains for multivariable controllers. This paper presents results from an application of these technologies to control design for linear models of an advanced turbofan engine. The objectives of the study were to transfer technology to industry and to identify areas of further development for the technology to be applied by industry to the design of practical controllers for high-performance turbofan engines. The technology elements and industrial development of tools to implement the steps are described with respect to their application to a GE variable-cycle turbofan engine. A set of three-input/three-output three-state linear engine models was used over a range of power levels covering engine operation from idle to maximum unaugmented power. Results from simulation evaluation of controller design, controller order reduction, controller scheduling, and integrator windup protection design are discussed and insight is provided into how the design parameter choices affect the results.