Motor Vehicle Level 3

Motor Vehicle Level 3

Anti-Lock Braking Systems

Resource 1

Motor Vehicle Level 3Resource 1

Aims


To introduce to ABS systems

Objectives

At the end of this lesson you should be able to:

1. Recognise the reasons for ABS systems within a light Vehicle2. Identify the main components within an ABS system3. Explain how an ABS controls the vehicle under heavy braking




•During emergency braking it can be difficult to control the vehicle due to the wheels locking up•ABS (Anti-lock Braking Systems) prevents the wheels from locking to reduce stopping distances. •Below is an example of a front wheel skid.



During skidding

•During a skid the skidding wheels have less traction than the non skidding wheels•By preventing the wheels from locking vehicle’s stopping time is reduced•The driver will also be able to control the vehicle under heavy braking



ABS Components

•Speed Sensors•Valve •Pump•Controller



ABS consist of the following components

Speed Sensors



Pump and Valves

•Pumps the brake fluid through the lines •Raises the pressure after it has been released.



ABS valves

•Position One: Valve is open and fluid is allowed to pass the brake•Position Two: Valve blocks the line isolating fluid from going to the brake (prevents pressure from rising further)•Position Three: Valve releases some pressure from the brake•The following shows the valve “holding the pressure” at the skidding wheel (Position Two)



One is included within each brake line controlled by the ABS, there are 3 positions:

Controller (E.C.U)

•E.C.U (electrical control unit) monitors the speed at all wheels in the vehicle to ensure that they are not under skid. •The ECU also reduces the pressure to the road wheels.



ABS Operation

•The control unit (ECU) will monitor the road wheels for a rapid de-acceleration (a skid is present). •The ECU will then stop brake pressure onto that wheel, allowing the wheel to move again•The ECU will then repeat this until the danger (skid) has passed.



ABS Types and Layout

•Four channel four wheel speed sensor •Three channel three wheel speed sensor•One channel, one wheel speed sensor



Four channel ABS system (most common)



Rise in Popularity in ABS systems



Summary - Have you?

• Recognised the reasons for ABS systems within a light vehicle?• Identified the main components within an ABS system?• Explained how ABS controls the vehicle under heavy braking?



Motor Vehicle Level 3

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