Study of RLS for Stability Margin Evaluation and Post Failure Data Analysis

This report presents results that demonstrate the application of time domain Recursive Least Squares (RLS) algorithm in flight control and testing. The RLS proposed here is based on the equation error principle and does not require any starting guess for its purpose. A post failure aircraft model estimation, for the purpose of reconfigurable/restructurable control, using RLS and recursive Discrete Fourier Transform (DFT) technique has been carried out. The evaluation shows the superiority of RLS over DFT in terms of computational load and convergence characteristics. Further a stabilized RLS algorithm, which can yield a useful alternative to covariance resetting as a solution to covariance wind-up in RLS has been implemented for post failure aircraft model estimation. A novel technique using RLS has been implemented to perform real time parameter estimation in absence of calibrated angle of attack and sideslip. Finally, the suitability of RLS for real time estimation of stability margin has been demonstrated. Simulated data has been used to demonstrate all these concepts.