Design of an active seat suspension for agricultural vehicles

Agricultural vehicle operators are exposed to intense vibrations mainly induced by soil unevenness. Since most of tractors are not equipped with any chassis suspension, the seat is the only system able to reduce the vibrations experienced by the operator. Traditional passive seats amplify vibrations at frequencies close to their natural frequencies. The first natural frequency of typical passive seats with an air spring and a hydraulic shock-absorber is between 1.5 and 4Hz. Thus their efficiency is poor for low frequencies and high amplitudes. In order to improve comfort of operators, active or semi-active suspensions for the seat can be introduced. An active suspension system for the seat of an agricultural vehicle relying on an active air spring is presented in this paper. The capability of the system of improving comfort of operators has been evaluated through simulations carried out with a validated model of the entire vehicle. Results of the proposed active suspension system are compared with ones provided by the passive suspension and the ones provided by an active system where the traditional passive shock-absorber is substituted by a controllable hydraulic actuator.