Application of a Weighted Average Surrogate Approach to Helicopter Rotor Blade Vibration Reduction

The advantages of employing multiple approximation methods and the effectiveness of weighted average surrogate modeling for approximation and reduction of helicopter vibrations is studied. Multiple surrogates, including the weighted average approach, are considered so that the need to identify the “best” approximation method for the rotor vibration reduction problem is eliminated. Various approximation methods are used to generate a vibration objective function corresponding to a flight condition in which bladevortex interaction causes high levels of vibration. The design variables consist of the crosssectional dimensions of the structural member of the blade and non-structural masses. The optimized designs are compared with a baseline design resembling an MBB BO-105 blade. The results indicate that (a) multiple surrogates can be used to locate low vibration designs which would be overlooked if only a single approximation method was employed, and (b) that the weighted average approach protects against the worst individual surrogate, while performing as well as the best individual surrogate. Furthermore, the surrogates were used in a global sensitivity analysis to identify the most significant design variables for the vibration reduction problem.