Time and Frequency Domain Identification of Jet Engine Dynamics: Problems and Solutions

Abstract

Identification of the fuel flow to shaft speed dynamics of a gas turbine is examined. Poor quality time domain models are obtained. This is shown to be a result of using a measured input signal for estimation, in order to exclude the actuator dynamics. This violates the underlying assumption of time domain estimation that the input signal is piece-wise constant. Errors are thus introduced into the time domain models. These conclusions are verified using simulations. High quality models are obtained using frequency domain techniques. These results have implications for all identification problems where a measured input signal is used.