Page - 43 - in Maximum Tire-Road Friction Coefficient Estimation

3 Vehicle model Table 3.1.: Overview of simulated manoeuvres and varied model parameters DLC Acceleration Deceleration Reference (all listed phenomena modelled) x x x No ARB x x x No wheel kinematics x x x and compliance Damper & spring linear x x x Steering ratio constant x Roll centre constant x Pitch centre constant x x No tire dynamics x x x Effective tire radius constant x x x Constant tire load x x x Wheel moment of inertia x x x deviation remains small in general. For longitudinal dynamics, both acceleration and deceleration manoeuvres were in- vestigated. Again, the friction potential µmax and the vehicle’s speed vx are varied. Reference speed profiles for each acceleration and deceleration are defined so that a cer- tainacceleration iskeptconstant. Thevehicle’s speedat thebeginningof themanoeuvre was not varied. To vary vx, the reference profiles were multiplied with integer factors. In case an acceleration or deceleration could not be reached because of µmax being to low, the simulation was stopped and not evaluated. For propulsion, the reference profile started just above vx= 0 with a constant bax=0.5 m/s 2 up to≈5 m/s2. For braking, the acceleration was varied between about 1 and 10 m/s2. A longitudinal control was used to follow the given speed profiles for these simulations. The investigated variables for the longitudinal manoeuvres include the longitudinal acceleration bax and the longitudinal velocity vx. Relative mean deviations for these two variables need to be small, in order to ensure small impact of the model variations. When focussing on investigations of the friction potential, accurate modelling of the horizontal tire forces is important. In total, vx, the wheel speeds ωi, the tire loadFz,i and the longitudinal tire forceFx,i are examined for each tire i. Thus, the longitudinal slips sx,i at each tire are implicitly evaluated. 43