ABSTRACT
Helicopters are notorious for their high vibration levels and the rotor systems are the main contributors to the problem. Rotor vibrations can be minimized by optimizing the rotor structure. However, the result of the optimization might require precise manufacturing of the rotor with tight tolerances leading to increased production cost and time. Moreover, due to loose manufacturing tolerances or wear from usage, the rotor might present higher vibrations during operation if the rotor vibration is sensitive to slight variations in the design variables. Hence, it is important to obtain a design point for minimum vibration that is also insensitive to such deviations. In this study, a four-bladed helicopter rotor is structurally optimized for minimum vibration and minimum blade mass. Along with these objectives, the sensitivity of each design point to variable deviations is calculated and combined into the objective function. It is aimed to obtain a design point resulting in minimum vibration and blade mass with the least variable sensitivity. Surrogate-based models are incorporated for the optimization to reduce objective function and sensitivity calculation times. For vibration minimization, vibration amplitudes along the rotor blades and at the rotor hub are considered. Furthermore, blade natural frequencies are separated from excitation frequencies to avoid any potential resonance. A comparative study is presented to provide the effect of parameter sensitivity.
