Braking action is required for every moving vehicle. The bicycles, motorbikes, cars, trucks and all other vehicles will have a braking system for stopping or to slow down the vehicle. Mechanical brakes, hydraulic brakes and electric brakes are different types of brakes available. Hydraulic brakes are most adaptable due to it's a safe and simple operation and uniform distribution of force. But, mechanical brakes are suitable for emergency and parking brakes. Electric brakes are faster and use the principle of electromagnetic forces.
But, recently all these conventional braking systems are replaced with ABS braking system. Anti-lock braking system or anti-skid braking system is a safety braking mechanism used in aircraft and other vehicles. ABS brakes use both electric and hydraulic controllers. This ABS system will eliminate issues like wheel lockup, slipping, loss of control and provides stability during excessive braking situations. Anti-lock brakes are most effective when you require sudden brakings and control of steering.
Maintaining steering ability, avoiding skidding, improving directional stability, and maximum braking are the advantages of ABS system. Anti-lock braking system working principle is based on threshold braking and cadence braking. These are techniques used by drivers for avoiding locking of wheels during sudden braking. Here, ABS will automatically perform these actions using the speed sensors integrated on each wheel. Anti-lock braking system function is to control the acceleration and deceleration of wheels by regulating line pressure.
Before discussing the working of the anti-lock braking system, we can learn some of the important components and their functions. Speed sensors, valves, pumps, and control units are the important components of this ABS braking system.
Also, Read: Basic Hydraulic System
Speed Sensors: The speed sensors attached to each wheel will monitor the speed and then determine the acceleration and deceleration. A voltage is generated in the sensor due to the rotation of wheels. Using this voltage, the signal (acceleration and deceleration) is transferred to the controller.
Valves: A valve is installed in every brake line controlled by ABS. Valves are used for regulating the air pressure to brakes during sudden brakings. Clogging(difficulty to open/close valve) is the only issue related to valves in the ABS system.
Pumps: When the valve releases the pressure, pumps will restore the pressure to the hydraulic brakes. The controller will adjust the pump for avoiding slipping and providing desired pressure.
Control Units: An ABS braking system will use both Electrical Control Unit(ECU) and Hydraulic Control Unit(HCU). The ECU will receive, amplifies and filter the signal from the speed sensors. These signals are passed to the HCU for applying or releasing the brakes.
Anti-Lock Braking System Working
Due to the rotation of wheels, magnetic fields are created around the speed sensors. The voltage generated due to these fluctuations is transmitted to the ECU. The controller will receive, amplify and filter these signals for calculating the acceleration and deceleration. On emergency braking situations, the wheel will decelerate at a faster rate and locks. When ECU finds a sudden decrease in speed, it will pass a signal to HCU. In such incidents, the HCU will close the valve and pressure to the brake pad reduces. This action will eliminate skidding or locking of wheels. This process will repeat 15 times in a second when the driven apply brakes in emergency conditions.