Modeling, design and investigation of seat suspension based on negative stiffness structure to improve the vibration environment for helicopter pilots

Abstract

The vibration transmitted to helicopter aircrew is the main risk factor for their health. In this paper, a seat suspension based on a negative stiffness structure is proposed to improve the vibration environment for the aircrew. The main advantage of the proposed seat suspension is mitigation of vibration transmitted to occupant in the same time keeping the system payload capacity. Hereafter deriving the dynamic model of the proposed system, the occupant model is attached to achieve an integrated occupant-seat-suspension model. Next, the design procedure of suspension parameters is presented to reduce the vibration transmission. In order to reach realistic results, the simulations are performed using the measured data on Bell-412 helicopter cabin floor. Then, the level of vibrations transmitted to seat and pilot body parts are evaluated using ISO-2631 and common criteria. The results show the performance of system based on negative stiffness structure is good in terms of vibration reduction so that root mean square and vibration dose value of vertical vibration for pilot’s body parts are mitigated about 40% in comparison with cabin floor vibration. Also, according to ISO-2631, comfort level is upgraded from uncomfortable to a little uncomfortable which represents promotion of ride quality and improvement of vibration environment for the pilot. Furthermore, the results indicate that no frequency modulation happens in the vibration transfer path from the cabin floor to the pilot’s head.