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MOTORING MADE SIMPLE
Technology to make stopping safe
While passive automotive safety features such as seat belts and pre-tensioners have become standard in cars available in India now, one other technology that is fast catching up is the Anti-lock Braking System (ABS). Many luxury cars come with ABS as standard fitment and even top-end variants of a few small cars offer ABS nowadays.
An anti-lock braking system, as the name suggests, focuses on preventing wheel lockup during the application of the brakes. Conventional brakes work on differential fluid pressure to activate either the brake callipers in a disc brake and/ or the brake pads in a drum brake. For the purpose, an elaborate network of tubing to carry the brake fluid to every wheel is set up and the brake pedal itself works like a kind of manual pump to increase the pressure of the brake fluid at the master cylinder located just behind the brake pedal. This, in turn, transmits the pressure to activate the pistons and cylinders in the disc brakes or drum brakes fitted to each wheel of the vehicle to eventually slow down the vehicle.
Most cars in India are front wheel driven and are fitted with discs in front and drum brakes at the rear. The trouble with conventional brakes, which depend on unregulated fluid pressure for braking, is that in the event of urgent stops, wheels tends to lock up. And since there is a constant buildup of fluid pressure at the piston-end, steady brake pressure leads to wheels locking up. This leads to skidding. And so, though the intention of braking hard is to stop the car, the vehicle continues to move forward due to its momentum. What is worse, skidding leads to the driver losing control of the vehicle.
Keeping the skid away
ABS' main purpose is to help avoid this skidding and in the process, allow the driver to retain control over the car. ABS equipment includes the conventional brake system hardware, but in addition, also features speed sensors at each wheel, a multi-position valve to control and vary brake pressure, a pressure pump to boost fluid pressure and an electronic controller that monitors the speed sensors and controls the valves.
ABS works by pumping the brakes of the car without actually locking the brake at each wheel. By boosting and varying the brake fluid pressure based on feedback from the speed sensor at each wheel, the disc brake's callipers or the drum's brake pads engage and disengage intermittently to stop the vehicle without wheel lock-up. The pulses of increased and decreased brake pressure are so fast that they are barely perceptible to the driver through the pedal.
ABS braking does not reduce braking distance by much, but definitely helps the driver retain control over the car during emergency braking. So, instead of the inevitable skidding and loss of control that is the characteristic of non-ABS cars, the driver of a car with ABS can also steer clear of the obstacle that he is trying to avoid. ABS also does not engage during regular, gradual braking or deceleration. It only engages during emergency high-speed braking. Yes, it really works!
S MURALIDHAR
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