Antilock Brake Systems ABS 1 ABS designed to

Anti-lock Brake Systems ABS 1

ABS • designed to prevent wheel lock-up to minimize stopping distance & help maintain steering control – by preventing wheel lock-up, tires will maintain traction with road surface • is also used on motorcycles and even trucks & buses with air brakes 2

ABS System

ABS Function

ABS Components 5

How Many Channels? • a channel describes a hydraulic brake line that is capable of being controlled by the ABS module 6

Wheel Speed Sensor • wheel speed sensor is a magnetic impulse sensor – works like a crankshaft position sensor • creates an AC voltage signal as the tone ring rotates with the wheel • the AC voltage signal frequency changes as the wheel speed changes 7

• AC voltage ripple frequency will change with wheel speed changes 8

Modulating Brake Fluid Pressure • • • Electronic Brake Control Modulator EBCM-activated solenoids modulate brake fluid pressure the solenoid valves can (while driver is stepping on pedal) either… – hold (maintain) pressure – dump (release) pressure – increase pressure – these solenoids can cycle the brakes 15 times/second Hold Pressure 9 Dump Pressure Increase Pressure proportioning valve is no longer needed!

Electronic Brake Control Module (EBCM) • 10 interaction between inputs, EBCM & outputs

ABS Modulator • may be attached to the master cylinder – integral ABS • may be mounted separate from the master cylinder – non-integral ABS 11

• schematic of brake lines and ABS components… 12