Ride quality evaluation: 8 d.o.f. vehicle model calibration

All road authorities try to obtain a good ride quality in their network, particularly with respect to the vibrations induced in the vehicles by road roughness. ISO 2631 defines the criteria to evaluate human whole body vibration (WBV) experienced by passengers during the ride, starting from the time history of recorded vertical accelerations in the vehicle; ISO standard also establishes vibration limits for discomfort, various activities, safety and health. The acceleration time histories also can be deduced by means of simulations of the motion, in which a vehicle model runs on measured pavement profiles. Simulations are useful to obtain global synthetic roughness indexes: for example, the I.R.I. (International Roughness Index) is the result of a simulation performed with a standard vehicle model, named “quarter car”. Nevertheless, in order to obtain a better evaluation of the ride quality of pavements, it needs to use more complex models, corresponding to real vehicles, after a calibration process. This process essentially consists in the comparison of the recorded vertical accelerations, achieved in real tests, with the results of simulations, varying model parameters. Simulations and real tests must be referred to a real vehicle, a reference road section, and various speeds. In this paper, the activities carried out to determine the parameters of a 8 D.O.F. vehicle model are presented; the result is a calibrated model, valid to obtain the time histories of vertical accelerations from the simulations, and to qualify the ride quality starting from geometric profiles of roads. Particularly, relating IRI and human WBV, simulations can be applied to plan the pavement management policies and to establish road roughness limits in various situations.