A Comparative Study of Integrated Vehicle-Seat-Human Models for the Evaluation of Ride Comfort

In the literature the value of the driver's head acceleration has been widely used as an objective function for the modification of the suspension and/or the seat characteristics in order to optimize the ride comfort of a vehicle. For these optimization procedures various lumped parameter Vehicle-Seat-Human models are proposed. In the present paper a Quarter Car model is integrated with three Seat-Human models with different levels of detail. The level of detail corresponds to the number of degrees of freedom used to describe the Seat-Human system. Firstly, the performance of the Quarter Car model, used as a basis, is analyzed in six excitations with different characteristics. Then, the performance of the three lumped parameter Vehicle-Seat-Human models are monitored in the same excitations. The results indicated that in the case of single disturbance excitations the Quarter Car model provided 50-75% higher values of acceleration compared with the eight degrees of freedom model. As far as the periodic excitation is concerned, the Vehicle-Seat-Human models provided values of acceleration up to eight times those of the Quarter Car model. On the other hand, in stochastic excitations the Vehicle-Seat-Human model with three degrees of freedom produced the closest results to the Quarter Car model followed by the eight degrees of freedom model. Finally, with respect to the computational efficiency it was found that an increase in the degrees of freedom of the Vehicle-Seat-Human model by one caused an increase in the CPU time from 2.1 to 2.6%, while increasing the number of the degrees of freedom by five increased the CPU time from 7.4 to 11.5% depending on the excitation.