汽车理论武汉理工课件

1、Chapter 5 Handling Performance汽车的稳定性5.1 Generalization （概述）5.2 Tire Cornering Property（轮胎侧偏特性）5.3 Linear Dual-freedom Mof Turning Vehicle（线性二自由度汽车模型对前轮角输入响应）5.4 Suspension and Cornering（汽车稳定性与悬架、转向系的关系）Definition of Handling Performance(汽车稳定性定义):An important performance to imply the easy of control

2、with the drivers will , or vehicle directional responsiveness to the negatives outside input which would bring rollover（翻车） or sideslip（侧滑） to the vehicle.(在驾驶员不感觉过分紧张、疲劳的条件下，汽车能按照驾驶员通过转向系及转向车轮给定的方向行驶，且当受到外界干扰时，汽车能抵抗干扰而保持稳定行驶的能力。)（ Handling performance belongs to the item of vehicle safety.）1. Conte

3、nt Input(输入) ： angle input角输入force input力输入Response(响应)：time domain response时域响应frequency-domain response频域响应。Yaw Velocity Gain frequency domain response characteristic横摆角速度频率响应特性Aligning performance回正性 Turning Radius 转向半径Turning portability转向轻便性Linear driving performance直线行驶性（lateral force sensitiv

4、ity侧向风敏感性、road uneven stability路面不平稳定性、Linear drivingperformance直线行驶性）Task Performance 典型行驶工况性能Ultimate drivingperformance极限行驶性能Snake speed: 59.6km/h(idle load) 57.3km/h(full load)body swayCockpit design philosophy is never to tilt设计的理念是驾驶舱永不倾斜cockpit驾驶舱MVariable speed emergency/（km h1）（idle load）Ne

5、w Accord97.3Mazda6120Audi A4124.9Audi A8131.6Variable speed emergency紧急变线速度2. Vehicle Axis System车辆坐标系zwrwuxw pwquyw p侧倾角速度(roll )u前进速度wq俯仰角速度( pitch)u侧向速度wr横摆角速度( yaw)w垂直速度）u forward velocity（前进速度） vside velocity （侧向速度） wvertical velocity （垂直速度）p roll angle velocity （侧倾角速度） q pitch angle velocity（俯

6、仰角速度r yaw angle velocity （横摆角速度）Velocity Form速度形式l 汽车时域响应分为稳态响应和瞬态响应。YawVelocityGain ofSteady-StateResponse转向阶跃输入下进入的稳态响应：等速直线行驶，急剧转动转向盘，然后维持转角不变，即对汽车施以转向阶跃输入，汽车经短暂的过渡过程后进入等速圆周行驶工况。YawVelocityGain ofInstantaneousResponse转向阶跃输入下的瞬态响应：等速直线行驶和等速圆周行驶两个稳态运动之间的过渡过程所对应的瞬间运动响应。Twr1wr 0td swtOvershoot(超调量) =

7、 wr1 wr 0 100%wr0:Steady State Yaw Velocity稳态横摆角速度e：Peak Value Reaction Time峰值响应时间s：Stabilizing Time稳定时间t：Reaction Time反应时间wr1:um Yaw Velocity最大横摆角速度certain steer angle转向盘转角dsw01.05wr 0twr (t)0.95wr 0esYaw Velocity Gain of Instantaneous Response转向阶跃输入下的瞬态响应Three-Phase Process( with a certain steer a

8、ngle inputsw0 ）1. Reaction Time (反应时间) the time used to reach the average yaw velocity(r0)firstly2. Peak Value Reaction time(峰值响应时间) the time used to reach the peak value of yaw velocity (r1)firstly3. Stabilizing Time(稳定时间)the time used to stabilizing the yaw velocity between 0.95r0 and 1.05r0 .d sw

9、= const.R , K 0：understeeringR , K0：neutral steeringR , K 0：oversteeringneutral steering：中性转向understeering：不足转向oversteering：过多转向 稳态转向特性：不足转向、中性转向、过多转向。 转向盘保持一个固定转角不变，缓慢加速或以不同车速等速行驶时，随着车速的增加，不足转向的汽车转向半径逐渐增大，中性转向的汽车转向半径不变， 过多转向的汽车转向半径逐渐减小。Real turning response of vehicle（汽车实际行驶情况）Low speed no lateral forces no slip angle the perpendicular(垂直的) from each of the wheels should pass through the same point (the center of turn)constant-radius turn (R0)High speed lateral accelerations lateral forcesslip angle R would changeCaused by tires and suspensionsUnder