Vibration reduction simulations of a lift-offset compound helicopter using two active control techniques

Abstract

This study attempts to alleviate numerically both the rotor and airframe vibrations of a lift-offset compound helicopter using two different active vibration control techniques. The XH-59A helicopter is considered as the lift-offset compound helicopter in the present work. The IBC (Individual Blade pitch Control) and AVCS (Active Vibration Control System) are applied to the lift-offset coaxial rotor and airframe, respectively, of the XH-59A to reduce vibration. Without or with IBC, the hub vibration of the XH-59A rotor is predicted using the rotorcraft comprehensive analysis code, CAMRAD II. For the AVCS simulation with a MIMO (Multi Input and Multi Output) model, various tools such as NDARC, MSC.NASTRAN, and MATLAB Simulink are used. At a flight speed of 200 knots, firstly, the 3/rev hub vibration of XH-59A rotor is reduced by 62% when IBC is used. Secondly, when AVCS is applied to the airframe, which is excited by the rotor vibratory loads reduced using IBC, the 3/rev longitudinal and vertical vibration responses at the specified airframe positions such as the pilot seat, auxiliary propulsions, and rotor-fuselage joint are reduced from 90.32 to 99.55%, when compared to baseline results without active vibration techniques.