Symmetry-Preserving Reduced-Order Wind Observers with Flight Test Results

Inferring wind velocity from aircraft motion is an enabling technology with applications in synthetic air data systems, path planning, safety monitoring, and atmospheric science. A reduced-order nonlinear state observer is developed to estimate wind velocity from aircraft motion. The observer is constructed by leveraging the symmetry of aircraft dynamics under the action of a Lie group to achieve global exponential convergence of the wind estimates to their true value. By only estimating the unmeasured wind and air-relative velocity, this reduced-order observer reduces computational complexity and simplifies nonlinear stability analysis. This approach eliminates the need for a small-perturbation assumption on the nonlinear dynamics yet casts the nonlinear wind estimation problem as the design of a linear, time-varying observer. Simulations and flight test results for a fixed-wing aircraft demonstrate the observer’s performance and robustness to unmodeled turbulence, aerodynamic modeling error, and measurement noise, highlighting its practical applicability and potential to ensure safe operation of future aircraft systems.