Vibration Suppression of Helicopter Blades by Pendulum Absorbers (First Elastic Mode of the Blade)
The pendulum absorbers have been used for suppressing the vibrations in helicopter blades. The aim of this study is to clarify the mechanism of the vibration suppression. But, most of the previous studies analyzed its characteristics based on the linear theory and explained focusing on the anti-resonance point. Since the pendulum may vibrate with large amplitude, it is expected that the nonlinearity have essential influence on its vibration characteristics. Therefore, we investigated the vibration suppression of a pendulum absorber considering its nonlinearity. In our first report, we proposed a 2-degree-of-freedom (2DOF) model composed of a rigid blade and a pendulum absorber. The blade is excited by giving a sinusoidal deflection at its end. In the second report, we proposed a 3DOF model by adding the fuselage, where the blade is also considered rigid. The blade is excited by a distributed force which changes sinusoidally. In this paper, a 3DOF model which is composed of a mass corresponding to a rotor mount on the fuselage, a flexible blade, and a pendulum is discussed. A periodic distributed force is given on the blade. This study clarified the mechanism of the pendulum absorbers for suppressing the vibrations of helicopters based on the nonlinearity theory.