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

Abstract

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.

Sensitivity Analysis of a Driver’s Lumped Parameter Model in the Evaluation of Ride Comfort

“…Sensitivity analysis is performed in a lumped-parameter model consisting of three parts: the vehicle, the seat and the human body in a seated position. For the simulation of the vehicle, a linear quarter-car model consisting of two DOFs is used [16]. The driver's seat is simulated with two DOFs [12]; for the seated human body, the four-DOF lumpedparameter model proposed by Boileau and Rakheja [14,17] is used.…”

“…The sprung and the unsprung masses are connected with a linear spring of stiffness k s = 20,000 N/m and a linear damper with a damping coefficient c s = 2000 Ns/m simulating the passive suspension system of a typical vehicle. The tire stiffness was modeled as a vertical spring with a stiffness coefficient k u = 160,000 N/m, while the tire damping coefficient was considered negligible, and no nonlinearities were considered [16,18].…”

“…In order to simulate different driving scenarios, different types of excitation are proposed in the literature [16,[19][20][21][22][23]. Single disturbance excitations are used to simulate local irregularities on the road profile, such as a speed bump or a pothole.…”

“…Both a speed bump and a pothole were simulated, separately, for the single-disturbance excitations. They both have a trapezoid shape, as presented in Figure 2, and their length is equal to 0.500 m. The height of the speed bump is equal to 0.010 m, while the depth of the pothole is equal to 0.040 m [16].…”

“…The periodic excitation was simulated as a sinusoidal function with an amplitude of 0.005 m [16] (Figure 3).…”