On truck tyre modelling

Sammanfattning: A physically based 3D tyre model with transient propertiesand reasonable computational effort is presented. Basic dynamitbehaviour is considered with the tyre belt modelled as a rigidring. Ground shear fortes are calculated with an anisotropicbrush model combined with a single sliding speed frictionfunction, introducing natural dependence between longitudinaland lateral forte. Using rigid ring residual stiffnessconsisting of higher radial belt modes enables driving overobstacles. An interface allowing different time steps forvehicle and tyre model is suggested. The model implemented as aFortran 77 program is capable of tunning in approx real time ona PC.Required model parameter values are obtained from staticmeasurements and modal analysis on a truck tyre. Compared tostatic measurements modal analysis is shown to be a powerfulmetbod also revealing resonances for the rim in the frecluencyrange of the tyre modes. Static measurements of tyre sidewallstiffness show linear characteristic and linear dependence withinflation pressure, which also holds when applied loads areequal to normal working loads.Steady state comering characteristic generated with themodel shows good agreement to truck tyre characteristicgenerated with Pacejka's magic formula. As in real tyres,transient simulation of lateral forte shows typical furst orderresponse to slip angle step change. The model also showsdifferent time constants for lateral forte and aligtringmoment.Truck based tyre forte measurements when running overobstacles show that the front axle beam compliance dominatesthe longitudinal dynamits. Simulation with a modified quartertar model coupled to the tyre model shows good agreement forthe vertical tyre forte. Prediction of wheel vertical distanceto road is excellent yet validation of longitudinal fortesshows only fair agreement.Keywords:tyre model, truck tyres, vehicle simulation,vehicle dynamits, transient response, modal analysis