Abstract
Keywords: Vehicle dynamics, vehicle handling, active traffic safety
Steady increase of the number of road accidents constitutes a serious problem of contemporary motorization. From many years, improvement of traffic safety has been an active research area. A popular strategy is to consider the system driver - vehicle - environment (DVE) as a closed loop control system. Road accident is a consequence of an erroneous functioning of particular components of the DVE system or a faulty cooperation among these components. It is widely understood that an important cause of traffic accidents is a lack of adaptation of vehicle handling properties to the skills and psychophysical abilities of the vehicle driver.
Vehicle handling properties depend on vehicle and its subsystems design parameters, as well as on tire characteristics and geometric and mass properties of the vehicle bodies. Handling properties can vary with the change of road adhesion parameters.
Vehicle handling properties are investigated through a multitude of road tests. Such investigations rely on recording vehicle behaviour during the execution of typical road manoeuvres that occur during vehicle exploitation and subsequent analysis of test results.
In parallel to on-road testing, the vehicle dynamic models are developed that facilitate studies of vehicle handling properties through the use of computer based numerical computations. Such studies limit the need for tedious and expensive experimental investigations. An enormous advantage of computer simulations is the ability to analyse the influence of vehicle design parameters on its handling properties. In particular, it is possible to simulate the stability and controllability tests in various road conditions and vehicle configurations. The conclusions that can be drawn from such studies, even if approximate, can be of great value not only at the stage of vehicle design but also during exploitation of various types of vehicles.
The author of this paper has been involved in the vehicle dynamics research aimed at the improvement of the active traffic safety. In the years 1994 - 2000, working with several large research teams, he developed a method for investigating vehicle dynamics that is characterized by a particular way of formulating the dynamic model of the vehicle. It relies on multilevel modelling of vehicle subsystems in the 3-D space. In the first phase, the mathematical model of the unconstrained vehicle body is formulated. Next, a chassis model is formulated, together with constraints describing wheel / tire interaction with road surface. Such an approach permits to easily introduce various tire models, suspension and steering systems. Owing to this approach, a universal mathematical description of the vehicle was conceived, with the block structure allowing the investigation of various configurations of chassis elements and their working conditions. In the framework of a research grant, the author developed a comprehensive 3-D model of a medium-duty dual axis truck that allows investigation of vehicle handling properties in complex road situations. The model can be used for studies aimed at improvement of vehicle active safety. The goal of this paper is to present the developed model of the truck, together with its validation by comparison with the results of extensive road tests.