汽車理論武漢理工課件

1、Chapter 5 Handling Performance汽車的穩(wěn)定性5.1 Generalization （概述）5.2 Tire Cornering Property（輪胎側偏特性）5.3 Linear Dual-freedom Mof Turning Vehicle（線性二自由度汽車模型對前輪角輸入響應）5.4 Suspension and Cornering（汽車穩(wěn)定性與懸架、轉向系的關系）Definition of Handling Performance(汽車穩(wěn)定性定義):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（翻車） or sideslip（側滑） to the vehicle.(在駕駛員不感覺過分緊張、疲勞的條件下，汽車能按照駕駛員通過轉向系及轉向車輪給定的方向行駛，且當受到外界干擾時，汽車能抵抗干擾而保持穩(wěn)定行駛的能力。)（ Handling performance belongs to the item of vehicle safety.）1. Conte

3、nt Input(輸入) ： angle input角輸入force input力輸入Response(響應)：time domain response時域響應frequency-domain response頻域響應。Yaw Velocity Gain frequency domain response characteristic橫擺角速度頻率響應特性Aligning performance回正性 Turning Radius 轉向半徑Turning portability轉向輕便性Linear driving performance直線行駛性（lateral force sensitiv

4、ity側向風敏感性、road uneven stability路面不平穩(wěn)定性、Linear drivingperformance直線行駛性）Task Performance 典型行駛工況性能Ultimate drivingperformance極限行駛性能Snake speed: 59.6km/h(idle load) 57.3km/h(full load)body swayCockpit design philosophy is never to tilt設計的理念是駕駛艙永不傾斜cockpit駕駛艙MVariable speed emergency/（km h1）（idle load）Ne

5、w Accord97.3Mazda6120Audi A4124.9Audi A8131.6Variable speed emergency緊急變線速度2. Vehicle Axis System車輛坐標系zwrwuxw pwquyw p側傾角速度(roll )u前進速度wq俯仰角速度( pitch)u側向速度wr橫擺角速度( yaw)w垂直速度）u forward velocity（前進速度） vside velocity （側向速度） wvertical velocity （垂直速度）p roll angle velocity （側傾角速度） q pitch angle velocity（俯

6、仰角速度r yaw angle velocity （橫擺角速度）Velocity Form速度形式l 汽車時域響應分為穩(wěn)態(tài)響應和瞬態(tài)響應。YawVelocityGain ofSteady-StateResponse轉向階躍輸入下進入的穩(wěn)態(tài)響應：等速直線行駛，急劇轉動轉向盤，然后維持轉角不變，即對汽車施以轉向階躍輸入，汽車經(jīng)短暫的過渡過程后進入等速圓周行駛工況。YawVelocityGain ofInstantaneousResponse轉向階躍輸入下的瞬態(tài)響應：等速直線行駛和等速圓周行駛兩個穩(wěn)態(tài)運動之間的過渡過程所對應的瞬間運動響應。Twr1wr 0td swtOvershoot(超調量) =

7、 wr1 wr 0 100%wr0:Steady State Yaw Velocity穩(wěn)態(tài)橫擺角速度e：Peak Value Reaction Time峰值響應時間s：Stabilizing Time穩(wěn)定時間t：Reaction Time反應時間wr1:um Yaw Velocity最大橫擺角速度certain steer angle轉向盤轉角dsw01.05wr 0twr (t)0.95wr 0esYaw Velocity Gain of Instantaneous Response轉向階躍輸入下的瞬態(tài)響應Three-Phase Process( with a certain steer a

8、ngle inputsw0 ）1. Reaction Time (反應時間) the time used to reach the average yaw velocity(r0)firstly2. Peak Value Reaction time(峰值響應時間) the time used to reach the peak value of yaw velocity (r1)firstly3. Stabilizing Time(穩(wěn)定時間)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：中性轉向understeering：不足轉向oversteering：過多轉向 穩(wěn)態(tài)轉向特性：不足轉向、中性轉向、過多轉向。 轉向盤保持一個固定轉角不變，緩慢加速或以不同車速等速行駛時，隨著車速的增加，不足轉向的汽車轉向半徑逐漸增大，中性轉向的汽車轉向半徑不變， 過多轉向的汽車轉向半徑逐漸減小。Real turning response of vehicle（汽車實際行駛情況）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