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Design and Flight Tests of an Adaptive Control System Employing Normal-Acceleration CommandAn adaptive control system employing normal-acceleration command has been designed with the aid of an analog computer and has been flight tested. The design of the system was based on the concept of using a mathematical model in combination with a high gain and a limiter. The study was undertaken to investigate the application of a system of this type to the task of maintaining nearly constant dynamic longitudinal response of a piloted airplane over the flight envelope without relying on air data measurements for gain adjustment. The range of flight conditions investigated was between Mach numbers of 0.36 and 1.15 and altitudes of 10,000 and 40,000 feet. The final adaptive system configuration was derived from analog computer tests, in which the physical airplane control system and much of the control circuitry were included in the loop. The method employed to generate the feedback signals resulted in a model whose characteristics varied somewhat with changes in flight condition. Flight results showed that the system limited the variation in longitudinal natural frequency of the adaptive airplane to about half that of the basic airplane and that, for the subsonic cases, the damping ratio was maintained between 0.56 and 0.69. The system also automatically compensated for the transonic trim change. Objectionable features of the system were an exaggerated sensitivity of pitch attitude to gust disturbances, abnormally large pitch attitude response for a given pilot input at low speeds, and an initial delay in normal-acceleration response to pilot control at all flight conditions. The adaptive system chatter of +/-0.05 to +/-0.10 of elevon at about 9 cycles per second (resulting in a maximum airplane normal-acceleration response of from +/-0.025 g to +/- 0.035 g) was considered by the pilots to be mildly objectionable but tolerable.
Document ID
20040008111
Acquisition Source
Ames Research Center
Document Type
Other - NASA Technical Note (TN)
Authors
McNeill, Water E. (NASA Ames Research Center Moffett Field, CA, United States)
McLean, John D. (NASA Ames Research Center Moffett Field, CA, United States)
Hegarty, Daniel M. (NASA Ames Research Center Moffett Field, CA, United States)
Heinle, Donovan R. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
August 21, 2013
Publication Date
April 1, 1961
Subject Category
Aircraft Stability And Control
Report/Patent Number
A-510
NASA-TN-D-858
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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