The Kineto-Dynamic Analysis And Optimal Design Using Suspension Seat-Human Coupled Model

Comprehensive amplitude and low frequency whole body vibration in operational vehicles can cause serious musculo-skeletal disorders among the exposed drivers. Suspension seat usually used as the driver seat for the off-road and heavy road vehicles. The suspension seat plays a vital role on attenuation vibration and shock transmitted to driver along the vertical axis. In the paper, kineto-dynamic analysis of the suspension seat-human coupled model and vehicle-specific optimal design for the suspension seat of the off-road vehicle are conducted.Firstly, the influence of the whole body vibration environment on drivers health and the effect of suspension seat are investigated. A kineto-dynamic model of a suspension seat is formulated to obtain relationship between the actual(axial) and effective vertical stiffness and damping characteristics. The proposed relations are verified through analysis of a two degree-of-freedom model of a cross-linkage air spring suspension seat neglecting the contributions due to seated body biodynamic in ADAMS. The model validity is also demonstrated using the experimental data. The model is used to identify optimal air spring coordinates to attain nearly constant natural frequency of the suspension, irrespective of the seated body mass and thereby the suspension equilibrium position. A methodology is further proposed to identify optimal damping requirements for vehicle-specific suspension seat designs to achieve minimal weighted objective function of seat effective amplitude transmissibility(SEAT) and vibration dose value(VDV) ratio. The shock and vibration isolation performance potentials of the optimal designs are evaluated and discussed considering standardized vibration excitation spectra of EM1, EM4, EM6, EM9 classes of vehicles superimposed with shock motions. Results show that the vehicle-specific optimal designs could provide substantial reductions in the SEAT and VDV values for all the vehicle classed considered. The proposed kineto-dynamic model and optimization method could thus serve as an important tool for designing vehicle-specific suspension seats.