Model Following Control of Gas Turbine Engines

As gas turbine engines become more complex, they also become more difficult to control. Classical control techniques and modern control theory such as multivariable optimal control have been used for design of engine control systems. Since these methods apply to linear time invariant systems, they suffer certain shortcomings when applied to the highly nonlinear gas turbine engine. In this paper, Liapunov’s direct method is used as the basis for a different approach to this problem. It is a technique specifically intended to deal with nonlinear systems. The resulting control system forces specified engine variables to track the corresponding variables generated in an ideal model of the engine. Results presented include a description of the design approach, its application to a generalized gas turbine engine with fuel flow and exhaust nozzle area as inputs, and data indicating the performance achieved when the control algorithm was tested on a detailed nonlinear digital simulation of the engine.