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The paper briefly presents two simulation models which describe the motion and dynamics of biaxial vehicles: a medium class car and 12 tons truck. The road surface may be even or uneven. The main models may be divided into coupled submodels. Their equations of motion can be derived separately. The programs can be run even on personal computers. The models are experimentally verified on even roads for typical manoeuvres recommended by ISO. The paper shows mainly the results of experimental evaluation of simulation models. It also presents steering system submodel in more detail. Its combination with other submodels describe small car motion and dynamics including the influence of steering system freeplay and dry friction.

The authors measure and simulate the vehicle motion in situations where typical defensive maneuvers in road traffic are being carried out, namely straight braking, double lane-change (overtaking), and ramp input on the steering wheel. They reproduce the vehicle motion (i.e. velocity, vehicle's C.G. trajectory and yaw angle) by using real records or by the simulated electronic data recorder (EDR) outputs. Thus, they operate in a way that is similar to that employed by forensic experts who analyze the EDR outputs. The employed method provides means of comparing the real or simulated exact values of velocity and of the vehicle's C.G. trajectory to the readings obtained by integrating the EDR outputs simulation. Estimation of the error, produced by the expert employing the EDR outputs, can be made in this way. The results show a possibility of occurrence of significant values of the error for simplified version of the device.

The article is the third one of series of the authors' SAE Papers (other two: 2002-01-0619, 2005-01-1261) concerning modeling and simulation studies of strong non-linear processes in a car steering system. Here, attention is concentrated on the stick-slip phenomenon caused by the dry friction. The studies focus on the influence of different kinds of friction force characteristics (from Coulomb-type to Stribeck-type) on the steering system dynamics. We present mathematical models and simulation studies of the stick-slip phenomena in a typical steering mechanism. The simulations concern the open loop tests (sinusoidal input and combination of ISO maneuvers) and provide materials for a sensitivity analysis (different friction models and vehicle motion conditions).

The paper presents a model derived for real time simulation. It has been applied in low-cost PC-based autoPW driving simulator built at the University of Technology, Faculty of Transportation, Poland. The following assumptions have been done: even, horizontal road surface, no vertical, pitch and roll vibrations of the body as well unsprung masses. The normal reactions of the road are described in quasi-static way. Compliances of steering system as well as description of six aerodynamic drag components are taken into account. The tire model is based on HSRI-UMTRI model with addition of aligning moment description. The model was experimentally verified.

The authors simulate the vehicle motion in situations where typical defensive maneuvers in road traffic are being carried out, namely straight braking, singular lane-change and “J-turn”. They reproduce the vehicle motion (i.e. velocity, vehicle's C.G. trajectory and yaw angle) by using the simulated “black box” outputs. Thus, they operate in a way that is similar to that employed by forensic experts who analyze the “black box” outputs. The employed simulation method provides means of comparing the simulated exact values of velocity and of the vehicle's C.G. trajectory to the readings obtained by integrating the “black box” outputs simulation. Estimation of the error produced by the expert employing the “black box” outputs can be made in this way. The body pitch and roll are sources of longitudinal and lateral acceleration recording errors because a gravitational acceleration component for the respective direction is added in simplified version of the device.

The paper presents mathematical models and simulation studies of a car handling with regard the freeplay (backlash, clearance) and friction (viscous and dry friction with stiction) in a steering system. For description of these principal non-linearities in equations of motion a new method (basing on two piecewise-linear projections luz(…) and tar(…) as well as their special mathematical apparatus) has been used. Simulation models describe lateral dynamics of a passenger car with typical steering system including the freeplay and friction. Three types of open-loop car tests (parking like, lane change and sinusoidal test) have been used in the simulation. Some examples of results are presented. They show a sensitivity of car dynamics processes on the freeplay and friction in the steering system.

The temperature influences significantly the braking effectiveness. The paper describes consistency criterions of the brake thermal state in road braking conditions and on the roll-stand. As a result of the vehicle motion simulation, the time histories of the heat fluxes generated on the friction surface of the front and rear disc were determined. They were used as an input data for the model of the heat transfer process in disc brakes. The problem was solved by the use of the finite element method. Time histories of temperatures on the friction surfaces and in the material of the disc were calculated. As a preliminary consistency criterion of the brake thermal state in road and roll-stand braking conditions, a balance of the energy cumulated in the brake rotor was assumed. As the most reliable consistency criterion an equality of average temperatures of the friction surface was assumed.

The article demonstrates selected issues related to assessment of computational accuracy in accident analysis. The hereto presented theoretical grounds of the methods make it possible to consider uncertainties in the assessment of input data values. The methods were compared on the basis of their exemplary application in the case of braking process study of a vehicle in rectilinear motion. Also for the aforementioned case, the results obtained by means of various computational methods of vehicle motion (analytical and simulation models) were compared with the outcome of the experimental study.

This paper continues a subject-matter of simulation studies of a car motion with inclusion of freeplay and dry friction, but in comparison to our SAE paper 2002-01-0619 (concerning to mechanical 2WS steering systems) in this paper also power assisted 2WS as well as 4WS steering systems are also the subjects of studies. The paper presents mathematical models and simulation studies of a car handling with regard to freeplay and friction in steering system. The models are customizable for several structures of steering system. Descriptions of freeplay and friction non-linearities base on special piecewise-linear projections. Elaborated models are used for digital simulation and sensitivity analyses concerning typical open road tests of passenger car. The paper describes these investigations and presents exemplary results. They show complexity of stick-slip phenomenon and car dynamics sensitivity on the freeplay and friction in the 2WS and 4WS structures.

”Tire blow-out” is a fast loss of air pressure that fills a vehicle tire, effecting from a puncture or a fatigue of tire structure. Statistical data, published in the United States, showed that “tire blow-out” caused more than 300,000 road accidents in the period of 1992–96 [1, 3]. Over 2000 people died in those accidents and many more were injured [1, 3]. The data and successful attempts of simulation presented in the work [1], prompted the author to try modeling and simulating this case of vehicle motion. The main emphasis in the hereto presented tests was put on qualitative assessment of vehicle behavior after a “tire blow-out”. The results presented in the work [1] show that the smallest motion disturbance of a vehicle takes place when the driver does not react (by turning the steering wheel or pressing the brake pedal). So, an assumption was made that the driver keeps a zero value of the steering wheel turning angle and pressure on the brake pedal.