Experimental and numerical investigation of a novel strut-mounted roller-screw inerter for helicopter vibration attenuation

A prominent problem of helicopters is the high vibrational levels due to the high-amplitude excitation forces originating from the main rotor. The ideal solution to reduce vibrations transmitted through the struts is to isolate the fuselage from the main rotor excitation at gearbox struts; therefore the overall vibration attenuation is achieved rather than local solutions. However, the limited available volume around the struts limits the application of existing vibration dampers. To solve the challenge, this work proposes a novel vibration attenuation idea that can effectively perform in confined spaces. Based on the inerter concept of roller-screw type, the axisymmetric design encloses the strut and shares its attachment points, providing a compact solution. The concept is demonstrated through experiments to identify realistic characteristics and rigorous numerical analysis using lumped-parameters and high-fidelity aeroelastic helicopter models to demonstrate vibration mitigation. The results show that the non-linear effects due to friction reduce the effectiveness at low excitation amplitudes; however, satisfactory vibration attenuation levels are achievable at high vibratory loads, a more critical condition for vibration alleviation performance.