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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.