汽车侧倾模型

Figure 2. Graphic presentation of the roll-equilibrium equation for a rigid vehicle The load transfer reaches oll angle in rigid model. From the graph, we can see the total vehicle reaction in decreasing and find the maximum lateral acceleration.
Figure 5.1. The load-transfer moments of the steer-axle, drive-axle, and trailer suspensions shown separately From the graph, three types of suspension are defined. (1) Suspension whose tires lift off before the peak point of the total moment (SBP). (2) Suspensionwhose tires lift off at the peak point of the total moment (SAP). (3) Suspensionwhose tires remain on the groundwhenthe total momentpeaks (SRP).
The Mechanics of Static Roll Stability
2014.11.18 1. Simplified Roll-Plane Model
Figure 1 presents a simplified model of a heavy vehicle in a steady turn in which the vehicle, its tires, and suspension have been “lumped” into a
Figure 1. A simplified free-body diagram of a heavyvehicle in a steady turn The equilibrium equation for roll moment about a point on the ground at the center of the track is: ������ w ∗ h ∗ ������������ = ������2 − ������1 ∗ − w ∗ g ∗ ∆������ (1) F2 − F1 ∗ is considered as the load transfer moment which is due to both 2 the side-to-side transfer of vertical load on the tire and the internal, compliant responses of the vehicle.The maximum possible value is w ∗ T/2. w ∗ g ∗ ∆������ is considered as the offset moment. Then here is going to discuss about several situations which will influence the static roll stability of heavy vehicle.
To this point, the discussion has assumed that all the tires and suspension of the vehicle may be “lumped” and assumed to operate as a single suspension. Figure 5.1 shows the load transfer moment and three suspensions of a tractor-semitrailer combination individually.
4. The Vehicle With Roll-compliant Suspension
The effect of roll compliance of the suspension is very similar to the effect of tire compliance except that the additional suspension roll motion takes place about a roll center which is typically above the ground. Figure 4.1 presents the suspension and tire roll center
Figure 4.1. Tire and suspension roll motion occur about different centers From figure 4.1, it’s apparent that the height of this suspension roll center has two influences. (1) For a given roll angle condition, the lateral displacement of the cg is less if the suspension roll center is higher. (2) For a given cg height, roll moment acting on the suspension due to the D’Alambert force is less if the suspension roll center is higher. Due to the two influences above, figure 4.2 shows the influence of stiffness of suspension and the height of suspension roll center on the roll stability.
Figure 3. Improving roll stability with a lower cg and a wide track
Lowering the cg height willdecrease the offset moment and widening the track will increase the load transfer moment. Both increase the total vehicle reaction and the roll stability.
T 2
2. Roller of The Rigid Vehicle
Begin by considering a completely rigid vehicle. Figure 2 is a graphic representation of equation (1) for such a vehicle.
Then, figure 5.2 illustrates the effect of stiffness of the three types of suspensions on the total moment and the vehicle stability.
Figure 5.2. Increasing the roll stiffness of different suspensions has different influences on roll stability. So, conclusions are drawn. (1) Increasing the stiffness of SBP doesn’t change the peak point of the total moment as well as the roll stability. (2) Increasing the stiffness of SAP can raise the peak point while it lowers the rollover angle ∅2 . (3) Increasing the stiffness of SRP can raise the peak point. If the stiffness ranges properly, ∅2 doesn’t decline which is desired for roll stability. Reference C. Winkle, Rollover of Heavy Commercial Vehicles, UMTRI Res. Rev 31(4) (2000), pp 1-13.
Figure 4.2. Improving roll stability with stiffer tires or suspension and by raising roll center of suspension
5. The Influence of Multiple Suspension
3. The Vehicle With Compliant Tires
Now consider a vehicle with compliant tires represented by linear vertical springs. Figure 3 illustrate how the rollover threshold is influenced by both cg height and track width.