Inflight investigation of the effects of rotor state measurement and feedback on variable stability helicopters
thesisposted on 23.05.2021, 17:04 by Marc David Alexander
This thesis describes a flight test evaluation of flight control laws applying rotor state measurements and feedback on the National Research Council Bell 412 Advanced Systems Research Aircraft (ASRA) and Bell 205A Airborne Simulator (AS). Parameter estimation of a higher-order mathematical model of the ASRA rotor dynamics was achieved by Maximum Likelihood Estimation (MLE) employing coupled rotor-body equations parameterized by explicit rotor and fuselage state measurements. Root Locus (RLM), Classical Multivariable (CMC), Eigenstructure Assignment (EAC), and Model Following control algorithms were implemented in Matlab/Simulink simulation for analysis of coupled rotor-body dynamics. Rotorcraft performance specifications were based on compliance with ADS-33E-PRF and Cooper Harper military handling qualities. Evaluated in desk-top and in-flight simulation, rotor state feedback of longitudinal and lateral disc tilt dynamics by modern multivariable control significantly improves inter-axis decoupling, disturbance rejection characteristics, rotor response dynamics, command tracking accuracy, and rigid-body bandwidth performance.