Study On The Influence From Vehicle’s Steering System On Controllability And Stability

The controllability and stability is one of the most important performance of vehicle, to which the most closely systems consists of the suspension and the steering system. This paper mainly studied the impact of steering trapezoid, wheel alignment parameters of the steering system on the self-aligning ability. The test methods included the K&C characteristic test and vehicle road test, which were simulated and analyzed with the help of ADAMS/ car in this paper.First, the formation reasons, design principles and influences on the control ability and stability of steering wheel positioning parameters were analyzed in this paper, and the obtaining of their calculation formula. The research objects included the toe angle, the camber angle, the caster angle, the kingpin inclination angle, the caster offset and the scrub radius.Second, the characteristic of the steering trapezoid was studied with the introduction of the Ackerman steering, and the relationship between the inside and outside wheel angle was discussed with the introduction of the general steering trapezoid. The characteristics of the general steering was introduced from the perspective of side-slip angle. In addition, the self-aligning torque of vehicle was analyzed from the point of wheel positioning parameters, including the composition, the forming reason, and the calculation formula was obtained in the end.Then, a certain vehicle model and a suspension assembly model were established with the help of ADAMS/Car. Finally, the simulations of K&C characteristic test and vehicle road test were made. The change rule of positioning parameters was gotten through the K&C characteristic test, which concluded that kingpin offset could easily change with the transformation of height and steering angle; kingpin angle could also be very vulnerable to the change of the height of wheel, while not the same to the change of the steering angle. Through the simulation of cornering-with-steer-release, it was concluded that the self-aligning torque was positively related to the steering angle; the process of cornering-with-steer-release was a closely straight condition after a series of circulation of self-aligning and over-self-aligning. Through the simulation of brake-in-turn, it was concluded that the greater the braking acceleration, the greater the self-aligning torque; the smaller the speed, the smaller the self-aligning, the greater the speed, the greater the self-aligning torque while the acceleration is constant.By the simulation of the constant-radius-cornering after changing of the scrub radius by changing the wheel position, it was concluded that the self-aligning torque of inside wheel would become greater and that of outside wheel become smaller with the positive increasing of scrub radius. By the simulation of the constant-radiuscornering after changing of the bottom length of steering trapezoid by changing location of the point, it can be concluded whether the scrub radius was positive or negative that. In the case that the trapezoidal bottom is long enough, the self-aligning torque was provided by both wheels, which mainly relied on the outside wheel. In the case of trapezoidal bottom is short, the self-aligning torque was provided by the outside wheel, while the inside wheel took the role of negative torque. The longer the trapezoidal bottom was, the more tendency that the inside wheel took more role. The relationship of the whole self-aligning torque and the trapezoidal bottom was a nonlinear curve with a maximum value. The maximum of the self-aligning torque was near the trapezoidal mechanism of parallel steering. The conclusion of this paper has an important directive significance on the design of the automobile steering system.