4.2 Braking Mechanics1.Ground Braking ForceuaMT,uF0XbrFpFXbFZ
a u FP FZ FXb T W Xb T F r 1 . Ground Braking Force 4.2 Braking Mechanics 1
1.Ground Braking ForceF小Ground Braking ForceFxb (frictional coupling betweenthe tire and road)> Definition: It is the braking force acting on the tires fromground along the X-direction.Z1WLXbrFpNote:1) Compared with the greatly increasing T,other torques are little enough to be ignoredwhen brakes work.2) T, is the braking torque from brakes2
Ground Braking Force—— FXb (frictional coupling between the tire and road) Definition: It is the braking force acting on the tires from ground along the X-direction. Xb T F r 1. Ground Braking Force—Fxb Note: 1) Compared with the greatly increasing Tμ , other torques are little enough to be ignored when brakes work. 2) Tμ is the braking torque from brakes. 2
2.BrakesBraking ForceF.> Brakes Braking Force-Fu(frictional coupling between theshoes and drum)> Definition: It is the braking force arising from the torque of thebrakes. acting on the edge of tire along the X-directionZFWurNote :1) F. is the test result on the test-bed2) F, has nothing to do with road condition.3
Brakes Braking Force——Fμ (frictional coupling between the shoes and drum) Definition: It is the braking force arising from the torque of the brakes, acting on the edge of tire along the X-direction. 2. Brakes Braking Force—Fμ Note : 1) Fμ is the test result on the test-bed. 2) Fμ has nothing to do with road condition. r T F 3
3.The relationship Between Fxb, F, and F0FLCFFxb=FPedal Force-Fp, NFxb ≤F,= Fz -0Pedal Force-F,, NLFxb = FlXxbmax = Fz βFis the limited force applied on the tires bythe ground foranti-skidpurpose.>Fxb can only increase to the limit of the frictional couplingbetween the tire and road
- Pedal Force FP，N F F F F Xb F F Xb C Pedal Force-FP，N 3.The relationship Between FXb, Fμ and Fφ Fφ is the limited force applied on the tires by the ground for anti-skid purpose. FXb can only increase to the limit of the frictional coupling between the tire and road. max Xb Z Xb Z F F F F F F 4
4. Slip of Tire(1)Definition> Slip of tireis defined by the ratio of slip velocity in the contactpath(forwardspeedminus(减去）tirecircumferential speed)to forward speed :usu...0roMSE0WuWwWWN00roV10小0usrolling : uw = Owro = s = 0Orolling & slipping : uw>Ow'rroslipping : w =0= s =100%(full locking)5
（1） Definition Slip of tire is defined by the ratio of slip velocity in the contact path (forward speed minus(减去) tire circumferential speed) to forward speed : 0 0 = w w r w w w r w r w u u r s u u r r u 0 0 : 0 & : : 0 100%( ) w w r w w r w rolling u r s rolling slipping u r slipping s full locking ＞ 4. Slip of Tire 5