Development of a Least Squares Time Response Lower-Order Equivalent Systems Technique
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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The most widely accepted method for specifying flying qualities of highly-augmented aircraft is the low-order equivalent systems technique. This technique matches the frequency response of a high-order system HOS with a lower-order equivalent system LOES. The LOES is generally in the form of a classical unaugmented aircraft so that comparisons with the classical data base can be made. Most LOES research has been accomplished using frequency response matching, however there are also methods available for matching the time responses of the HOS and LOES. Time response matching is an attractive option for flight test applications since all that is required is output versus input data. This thesis develops and tests a Least Squares LOES time response matching program. The program was tested analytically at the Air Force Institute of Technology, Wright-Patterson AFB, OH. During the analytical testing, a HOS was modeled using an A-4D aircraft with servo-actuator and feel system dynamics. Lower order equivalent parameters were calculated using the Least Squares program and the results were compared to those obtained using a frequency response matching program LONFIT. Various flight conditions and feel system dynamics were used to change the HOS dynamics and the effects of these changes on the two matching techniques were investigated.
- Attack and Fighter Aircraft