Drive Smart: Auto Info....

The all-new informative 'Drive Smart' segment of this blog is to bring you info on features of your automobile. Know what you drive...

The Anti-lock Braking System

ABS Logo

The everyday ABS or known as anti-lock braking system is widely used on nearly every new car to date. Despite that, only a handful know the purpose and function of ABS braking systems.

ABS in general is used to improve control over a vehicle. Modern ABS systems not only prevent wheel lock whilst braking but also enables electronic control of brake force distribution also known as EBD(Electronic Brake-force Distribution).

Early Systems...

Image courtesy of hemmings.com
First mechanical ABS system on the Jensen FF

Back in the 1960s, a fully mechanised ABS system was developed for only handful of cars such as the Ferguson P99 race car and the Jensen FF. The production of these systems were short lived as they were very unreliable and costly to produce. 

Modern Integrations

The first four wheel ABS system was used on the 1971 Chrysler Imperial, developed by the Chrysler and Bendix Corporation. A three-channel, four wheel sensor system known as "Sure-Brake" that can detect and prevent wheel slip to increase driver control over the vehicle. The system (over years of usage) proved reliable and so the modern ABS system was born. 

In 1970, the Ford Motor Company added ABS to the rear wheels of their Lincoln Continental's as an option which became standard in 1971 known as "Sure-Track" with General Motors following after with the "Trackmaster" ABS system. Within the same year Nissan launched the "Electro Anti-lock System" known as EAL which became Japan's first electronic ABS system. 

Components Of ABS And How They Function...

The system is comprised of 4 main devices:

1. Speed Sensors
2. Valves
3. Pump
4. Controller

Speed Sensors

The speed sensors are used to detect acceleration and deceleration in speed. These sensors use a magnet and a steel coil to generate a signal. The rotation of the wheel creates a magnetic field around the sensor which then generates a voltage in the sensor. The voltage is created by the rotating wheel and changes in speed will affect the level of voltage created.

Valves

Valves are present in each and every brake line controlled by the ABS. On some systems the valves have three positions. 

1. Position one, valve is open which enables direct pressure from master cylinder to the brakes.
2. Position two, valves is closed which isolates pressure from the master cylinder. This prevents any more pressure being applied to the brakes when the driver steps the brake pedal harder.
3. Position three, Valves are partially open to enable some brake pressure to flow. 

Pump

The pump in the ABS system is used primarily to restore pressure from the hydraulic brakes after the valves have released it. A signal from the speed sensors will release valve at the detection of wheel slip. The pump will be used to modulate brake pressure in order to provide the desired amount of pressure and reduce slipping. 

Controller

The controller is an ECU based unit which receives data and information from each and every one of the wheels speed sensors. If a wheels slips and loses grip, the controller will release the valve. The controller will then limit the brake force and distribute the brake pressure evenly throughout the wheels (EBD) and activate the ABS modulator which actuates the braking valves.