The tire model Mechanical Engineering（机械工程的轮胎模型）.pdf

The tire model Tires are perhaps the most important, but difficult to model, component of an automobile. In addition to supporting the vehicle and damping out road irregularities, the tires provide the longitudinal and lateral forces necessary to change the speed and direction of the vehicle. These forces are produced by the deformation of the tire where it contacts the road during acceleration, braking, and cornering. Aligning Moment, Mz Slip Angle, α Velocity Lateral Force, Fy Figure 1: Tire operating at a slip angle. In the absence of side forces, a rolling tire travels straight ahead along the wheel plane. During a cornering maneuver, however, the tire contact patch “slips” laterally while rolling such that its motion is no longer in the direction of the wheel plane (Figure 1). The angle between its direction of motion and the wheel plane is referred to as the slip angle, α. This lateral “slip” generates a lateral force, F , at the tire-ground interface. y Because the force acts slightly behind the center of the wheel, it produces an aligning moment, M , which tends to realign the wheel in the direction of rolling. z Normal cornering maneuvers result in small slip angles, low lateral force, and minimal sliding of the tire. At larger slip angles lateral force increases and reaches a maximum as the tire begins to slide. Figure 2 illustrates the relationship between lateral force and slip angle for a typical tire. For small values of α—say, less than four degrees—the relationship is nearly linear. The initial slope of the curve is known as the cornering stiffness, C , described in units of force per degree.