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Flight Control System Design and Analysis

DCI personnel are major players in the development of the SLS flight control system performing design, analysis, and flight software functions to ready the vehicle for flight.  The SLS autopilot design challenge is to maintain stable and high performance control of the vehicle in the presence of uncertain disturbances and dynamics such as thrust misalignment, sloshing propellant, structural elasticity, and varying atmospheric winds. SLS flight control activities include development of control system architecture, selection of optimal control parameters, high fidelity time and frequency domain analysis, writing flight software pseudo-code/algorithms, and maintenance of NASA revision controlled analysis tools.  

DCI personnel develop frequency and time domain gain optimization techniques to determine the control parameters which yield an optimal balance of stability and performance objectives.  

 

Figure: Constrained P-D gain optimization with angle of attack response as a performance objective.

 DCI flight control system activities includes development, parameter tuning, and flight testing of the SLS adaptive augmentive control (AAC) algorithm.  DCI develops and generates time domain simulation cases to demonstrate the efficacy of and support the rigorous evaluation of the adaptive algorithm on control performance.


Figure: Simulation result of the AAC algorithm preventing the growth of an unstable flex mode.

The SLS algorithm including AAC was flight tested on the Dryden Flight Research Center (DFRC) F/A-18 Full-Scale Advanced Systems Testbed (FAST) during early 2013, early 2014. Activities in support of the flight test included: generation of SLS test scenarios, system identification and de-stabilization of the F/A 18 structural dynamics, and analysis of flight test data versus pre-flight predictions.

 

Figure: Depiction of SLS-like trajectory flown by the SLS Flight Control System on the F/A-18 during SLS AAC flight test.


Figure: System identification of the fundamental bending mode on the F/A-18 AAC Flight Test Platform.



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