Anti-lock braking system

 

What is an Anti-lock braking system?

Anti-lock braking system, commonly known as ABS is a safety feature in modern vehicles. It helps drivers control their vehicles during hard braking or emergency stops. ABS works with a regular brake system to prevent the wheels from locking up and skidding which involves to loss of steering control and accidents.

Anti-lock brake systems were initially tested for railway cars and aircraft in the 1950s. The world’s first Formula car was incorporated with the ABS system in the 1960s. After that, Mercedes-Benz began to install the ABS system into commercial vehicles. After a few years back, they revealed technology. Then the ABS system was included in many cars.  Therefore, ABS is a standard feature of modern vehicles to enhance vehicle stability and control.

ABS is mainly effective in slippery conditions, such as rain, ice or snow which needs traction control. During the sudden stopping, there is a possibility to loss of traction between the tires and the road surface. It increases risks of skid and loss the control of steering. This leads to accidents. When such kind of situation, the ABS comes to the rescue.

Anti-lock braking system includes four main parts,

Speed sensors

Pump

Valves

Controller

Speed Sensors

Speed sensors provide wheel speed in an Anti-lock braking system. These sensors are located at each wheel or differential. It takes action to provide speed when the wheels are going to lock up.

Pump

Pumps restore pressure back to the system when the valve releases the pressure from the brakes.

Valves

The valve in the system allows three positions to allow, block and release pressure on the brakes. In the first position, the valve passes pressure from the master cylinder to break through the valve opening. Secondly, the valve isolates the master cylinder and brake to prevent pressure from rising. Finally, the valve releases some of the pressure from the brake.

Controller

The electronic control unit (ECU) takes data and processes the data. Then it gives real-time commands to control the braking pressure according to the wheel-speed sensor data. This is known as the computer in the car.

How it works

In this system, the ECU always monitors the wheel speed through wheel-speed sensors for rapid deceleration. In this kind of situation, the wheels lock up. ECU knows that wheels cannot have such a kind of deceleration. Before the locking wheels, Wheels need to be stopped quickly to prevent accidents. The ABS controller gives commands to reduce pressure to the brakes until the wheel acceleration again and then increase the pressure until the wheels decelerate again. This is done very quickly before reducing wheel speed suddenly. This is happening to slow down the wheel speed at the same rate as the car.

Modulation of Brake Pressure: The special thing is that the electronic control unit can maintain the brake pressure of each wheel independently. This allows the maximum braking power to the car. The system rapidly increased and decreased brake pressure when necessary to prevent skidding.

Pulsating Brakes:  while operating ABS, the driver feels a pulsating or vibrating sensation through the brake pedal. This is a normal condition that indicates the ABS works correctly to prevent the wheel from locking up.

Steering Control: ABS helps to maintain the stability of the vehicle during the rapid braking through the ABS system. This allows steering control by preventing wheel lock-up.

Anti-Lock Brake Types

Four channel, four sensor

This system has four individual sensors and four valves for each four wheels. System monitor all wheels separately. This is the best system and it gives maximum braking force to the vehicle. Also, Four-channel ABS system gives better traction control.

Three channel, three sensor

This system consists three sensors and three valves. Two front wheels have individual sensors and valves while both rear wheels have one sensor and valve. For rear wheels, it is positioned in the rear axle to monitor both wheels together. This system commonly can be seen on pickup trucks with four-wheel ABS. The front wheels can achieve maximum brake force due to sensors monitor front wheel individually. However, rear wheel are monitored together. Therefore, there is a possibility to only one wheel before lockup.

One channel, one sensor

This system only has one sensor and one valve for rear wheels. This is commonly seen in pickup trucks with rear ABS. The sensor is located in the rear axle. One-channel ABS system works same as the rear end of three-channel ABS. There is a possibility to only one wheel before lockup by reducing the braking effectiveness.

Advantages and Disadvantages of ABS

Advantages	Disadvantages
Low wearing brake pads and brake discs	maintainance cost is high
Vehical can be controlled at heavy braking	high complexity of the system
avoid uneven tyre wear due avoiding lockup wheels	braking distance may vary on different surface conditions
Due to smooth braking conditions, vehicle is running smoothly
Enhanced Traction