Improved simulation and validation of road vehicle handling dynamics

This research is on evaluating and improving vehicle handling dynamics computer simulations. A simulation validation methodology, based on the comparison of simulation predictions with actual vehicle field test results, has been developed. To provide a basis for this work, experimental testing of four vehicles was performed; with results being compared with predictions made by two existing vehicle stability and control simulations. Simulation performance was examined in the steady state and transient regimes of the time domain, and in the frequency domain.; The two simulations, Improved Digital Simulation Fully Comprehensive (IDSFC) and Vehicle Dynamics Analysis Non-Linear (VDANL), contain nonlinear, lumped-parameter, models of the vehicle body, steering system, and suspension system, and include empirical models to represent nonlinear behavior of the tires. The simulations were evaluated in a fixed-control steering mode.; Using the validation methodology developed, the simulations were evaluated using both qualitative and quantitative measures. This evaluation showed where the simulation predictions agreed or disagreed with experimental results, and was used to identify regions from the range of vehicle handling maneuvers for which the simulations provided reliable results. For this research, particular attention was given to improving simulated yaw rate response to steering inputs.; Deficiencies in the modeling of tire dynamics and the steering system were identified as two major causes of the simulations' inadequacies. The dynamic responses of the tires, while having no effect on steady state simulation predictions, were found to have a very large influence on transient simulation predictions.; An improved tire dynamics model, using a second-order system model, was developed and implemented. This model more accurately represents dynamic tire side force and aligning moment response to steering inputs, and improves the simulated transient and frequency responses.; Also, a revised steering model was developed. This model includes the effects of steering system free play as well as the effects of power assisted steering. Both of these effects were found to contribute significantly to improving simulation predictions in the steady state, transient, and frequency response domains.; In conclusion, the validation methodology presented provides a useful tool for evaluating vehicle dynamics simulations, and the improvements made to the tire and steering system models have advanced the state-of-the-art of vehicle dynamics simulation.