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Study of a Simulation Tool to Determine Achievable Control Dynamics and Control Power Requirements with Perfect TrackingThis paper contains a study of two methods for use in a generic nonlinear simulation tool that could be used to determine achievable control dynamics and control power requirements while performing perfect tracking maneuvers over the entire flight envelope. The two methods are NDI (nonlinear dynamic inversion) and the SOFFT(Stochastic Optimal Feedforward and Feedback Technology) feedforward control structure. Equivalent discrete and continuous SOFFT feedforward controllers have been developed. These equivalent forms clearly show that the closed-loop plant model loop is a plant inversion and is the same as the NDI formulation. The main difference is that the NDI formulation has a closed-loop controller structure whereas SOFFT uses an open-loop command model. Continuous, discrete, and hybrid controller structures have been developed and integrated into the formulation. Linear simulation results show that seven different configurations all give essentially the same response, with the NDI hybrid being slightly different. The SOFFT controller gave better tracking performance compared to the NDI controller when a nonlinear saturation element was added. Future plans include evaluation using a nonlinear simulation.
Document ID
19980221026
Acquisition Source
Langley Research Center
Document Type
Technical Memorandum (TM)
Authors
Ostroff, Aaron J.
(NASA Langley Research Center Hampton, VA United States)
Date Acquired
September 6, 2013
Publication Date
August 1, 1998
Subject Category
Aircraft Stability And Control
Report/Patent Number
NAS 1.15:208699
NASA/TM-1998-208699
L-17767
Funding Number(s)
PROJECT: RTOP 522-21-61-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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