An Evaluation of Frequency Domain Ensemble Averging to Improve Aircraft Stability Derivative Estimation
AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH SCHOOL OF ENGINEERING
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This research evaluated a process to improve aircraft stability derivative estimation results. The Have Derivatives process used overlap ensemble averaging in the frequency domain to minimize noise on the original time domain signals. The process estimated average complex frequency response functions that were then transformed back into the time domain as a set of discrete pulse responses with far less noise than the original signals. These clean signals were used in a parameter estimation program to estimate better stability derivatives than were estimated with the original noisy signals. Both simulation and flight test data were used to study the effects of various noise levels on stability derivative estimation results and to evaluate the Have Derivatives process to improve those results. The simulations demonstrated dramatic improvement using the Have Derivatives process. The flight test results were not as conclusive. The ensemble averaging step of the Have Derivatives process was not effective enough at reducing noise on the flight test data due to non-uniform frequency content of the flight test input. The overall recommendation was to further evaluate the Have Derivatives process using a broadband flight test input, similar to the input that worked well in simulation.