To start with this series of articles, we should keep one thing in mind, and that is - Everything apart from Safety, comes second, be it the looks, performance, efficiency or brand. Safety is the foremost thing, when one is driving a car. And our aim of this series is to help readers, understand better about various safety systems available in the cars.
Our very first introduction to you with safety systems will be the ABS or the Anti Lock Braking system, one of the oldest and the most efficient mechanism in a car. So, how does an ABS work, what are its types or what is an ABS, we will address all your doubts.
What is ABS?
ABS or Anti Lock Braking System, as the name confirms, prevents wheels from locking, in the event of hard braking. The theory behind anti-lock brakes is simple, when we brake hard, the tyre locks, which enable wheel skid. A skidding wheel has less traction than a non-skidding wheel and hence the vehicle loses the control. What is traction, you may ask? Take this for an example, you are stuck on ice, and you are revving hard to go forward, instead, your wheel keeps rotating in a single place, which means there is no traction on the wheel. The ABS prevents the wheels from skidding, helping you to control your vehicle by slowing down as well as by steering it.
Science behind ABS
Science is everywhere and we can't ignore it! So is the case with the Anti Lock Braking system. To understand why we need ABS in our cars, we first need to understand the basic science. And Friction and Momentum are two words, which explains the whole thing. When we brake hard, our wheel stop rotating and instead slides. This happens because the Rolling friction comes into play, the friction between two objects that aren't moving relative to each other).
Above is the formula for Friction, where N is the normal force and mu is the friction coefficient. Rolling friction coefficients are larger than the coefficients of kinetic friction, which means if a vehicle is under the influence of rolling friction instead of kinetic friction, it will take less distance to stop. But, when one hit the brakes at high speeds, the car comes in the influence of kinetic friction and the momentum further gives it a push, making hard to control the vehicle.
ABS at Work
ABS is made to detect the above mentioned skidding phenomenon and control it. The process is controlled by sensors, which after realizing, there is only deceleration in the wheel that are out of the ordinary, right before the wheel locks, releases the pressure from the brakes. This in return again increases the speed of the wheel.
The whole process is very rapid, to a tune of engaging and disengaging the brakes upto 15 times per second. The result is that the tyre slows down at the same rate as the car, giving the system maximum braking power. One can sense pulsing feeling in the brake pedal when the ABS is in operation.
Components of ABS
There are four main components to an ABS system:
Speed Sensors: Sensors, like in any other system, are meant to sense any out of the line activity and they do the same in the ABS. Speed sensors, located at each wheel, provide information about wheel lock-up, which is to be prevented at any cost.
Valves: Valves are meant to control the pressure of the fluids, which operates the calipers of the brakes. There are valves for each brake in the brake line, controlled by ABS. Valve in position 1, is fully opened and the fluids can pass through the brake completely. In position 2, the valves are completely closed, blocking the pressure, even if the driver pushes brake harder and in the final position, it is partially opened.
Pump: When a valve reduces the pressure in a line, the pump is there to get the pressure back up.
Controller: The controller is a computer in the car. It watches the speed sensors and controls the valves.
Anti-Lock Brake Types
There are basically two kinds of Anti-lock braking systems, depending on the type of brakes in use.
Four-channel, four-sensor ABS
As the name suggests, there is a speed sensor on all four wheels and four valves each for all wheels. With this setup, the controller monitors each wheel individually to make sure it is achieving maximum braking force.
One-channel, one-sensor ABS
In this system, only rear wheels come loaded with ABS and easy to identify. There is one brake line going through both rear wheels and the speed sensor is near the differential on the rear-axle housing, and can be identified by looking for an electrical connection there.
While this is a detailed discussion on ABS, we also did a preface for the ABS few months ago!