Fuselage Vibration Reduction Simulations using Individual Blade Pitch Control for a Lift-offset Compound Helicopter

This paper investigates the use of active rotor vibration control, specifically individual blade pitch control (IBC), for a 13 600 kg (30 000 lb) class lift-offset compound helicopter to simultaneously reduce rotor and fuselage vibration responses while enhancing rotor performance. The rotor and fuselage systems are modeled and analyzed separately using CAMRAD II and MSC.NASTRAN respectively, and a one-way coupled analysis is applied to account for the effects of rotor hub vibratory loads on the fuselage. The study trims the isolated lift-offset rotor using a propulsive trim approach, predicting rotor vibration and performance metrics under IBC conditions. Fuselage vibration responses are also analyzed with IBC applied to the rotor. The optimal IBC input scenario, employing multiple harmonic inputs, is determined using a cost function (F) aimed at minimizing both rotor and fuselage vibrations while improving rotor performance at a forward speed of 250 kn. Simulation results demonstrate that applying a specific multiple harmonic IBC input condition (2P/0.5°/0° + 3P/0.5°/225°) achieves significant improvements: rotor vibration (VI) is reduced by 50.67 %, fuselage vibration responses (J) are lowered by 42.23 %, and rotor performance (L/Dsube/sub) is enhanced by up to 4.16 %.