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