Comparison of optimization methodologies for robust feed-forward controller for gust load alleviation system
Sandesh, Gowridedda Sundaresh
Date of Issue2016
School of Mechanical and Aerospace Engineering
The master thesis work done by the author encompasses the design of a robust feed-forward controller for gust load alleviation based on optimization techniques to reduce the wing-box mass. The control methodology developed in this thesis is independent of the aircraft platform and can be implemented any aircraft. The author considers H2 and L00 norms in the cost function and synthesizes an optimal feed-forward controller. The actuator limits (rate and deflection) and load factor limits for passenger safety are included in the constraints of the optimization process. The optimization process is carried out after determining the worst case load scenario across the complete flight envelope and synthesizing the controller based on that scenario so as to be robust for all fuel, mach and dynamic pressure variations. The controller synthesized from the optimization process is transformed and reduced to a lower order Infinite Impulse Response (IIR) filter from a higher order Finite Impulse Response (FIR) filter. The IIR filter is further provided with a roll-off for eliminating high frequency oscillations in the actuator. The robustness analysis is carried out by performing Monte Carlo simulations for various parameter uncertainties. The controller was synthesized on a linear model (longitudinal dynamics only) with six elastic modes and it is validated on a linear model (longitudinal and lateral dynamics) with nineteen elastic modes which includes non-linear actuators.