Vibration transmissibility behaviour of high order biodynamic models used in vehicle seat design

The effects of vibration transmissibility using high order biodynamic models of four, five and seven degrees of freedom that can replicate a human body exposed to vibration transmissibility while driving was investigated to identify resonant frequencies associated with injury. It was found that these models address vehicle seat deformities and represent the body hop motion when driving. The five degree of freedom models provided the best results to approximate resonant frequencies associated with the legs, lower torso, spine and whole body vibration at the seat person interface, while the driver's hands were on the steering and was supported with a backrest. The four degree of freedom model excluding the backrest was able to replicate experimental data and a sensitivity analysis of the stiffness and damping parameters indicated that this model was more robust compared to the others, and could predict whole body vibration to accommodate for intra subject variability. Non-linear damping and stiffness properties were noticed for acceleration magnitudes greater than 1g root mean square (rms) and for high order models, which provide greater anatomical description to predict injury in contrast to simple models that have large lumped masses to represent the upper and lower torso. In addition, biodynamic models greater than seven degrees of freedom can be utilised with non-linear stiffness and damping techniques to predict vibration and impedance behaviour for greater number of body ligaments applied to old seats or retrofit seat design applications.