16-10-2012, 05:57 PM
Anti Lock Braking system (ABS)
report of ABS.doc (Size: 775 KB / Downloads: 24)
ABSTRACT
Anti Lock Braking system is a system on motor vehicles, which prevents the vehicle from locking while braking. Anti Lock Braking system (ABS) is a very important safety feature, because vehicles become very unstable when the vehicles are locked, braking becomes inefficient, and so braking distances become very long. A typical ABS is composed of central electronic unit, four speed sensors, and two or more hydraulic valves on the brake circuit. The electronic unit constantly monitors the rotational speed of each wheel. When it sensors that one or more wheel is rotating slower than the others moves the valves to decrease the pressure on the braking circuit, reducing the braking effect on that wheel.
The ABS equipment may also be used to implement traction control on acceleration of the vehicle. If when accelerating, the tire looses traction with the ground, the ABS controller can detect the situation and apply brakes to reduce the acceleration so that traction is regained. Manufactures usually offer this as a separately price option even though the infrastructure is largely shared with ABS. More sophisticated versions of this can also control throttle levels and brakes simultaneously, leading to what is termed as the Electronic Stability Program.
INTRODUCTION
Anti Lock Braking system was first developed for aircraft. The first ABS for automobiles was developed by Robert Bosch, becoming available in the year 1978. They first appeared in trucks and limousines from Mercedes-Benz. Systems were later introduced on motorcycles. Like a conventional braking system, ABS is more effective when the tires are in good operating condition with good tread and correct tire pressure is maintained. Like any vehicle whether equipped with ABS or not proper seat adjustment is important. Position yourself comfortably for maximum effectiveness with your ABS. For commercial applications the load should be evenly distributed over the rear axle for maximum effectiveness of the ABS.
PRINCIPLES OF SIMPLE BRAKING SYSTEM
The basic principle of brake system is:
1) Friction: Friction is a measure of how hard it is to slide one object over another. The brakes transmit the force to the tires using friction, and the tires transmit that force to the road using friction also.
2) Hydraulics: The basic idea behind any hydraulic system is very simple. Force applied at one point is transmitted to another point using an incompressible fluid, almost always an oil of some sort.
3) Leverage: The pedal is designed in such a way that it can multiply the force from your leg several times before any force is even transmitted to the brake fluid.
In the figure above, a force F is being applied to the left end of the lever. The left end of the lever is twice as long (2X) as the right end (X). Therefore, on the right end of the lever a force of 2F is available, but it acts through half of the distance (Y) that the left end moves (2Y). Changing the relative lengths of the left and right ends of the lever changes the multipliers.
TYPICAL BRAKING SYSTEM
1) Disc Brakes: Disc brakes use a clamping action to produce friction between the rotor and the pads mounted in the caliper attached to the suspension members. Inside the calipers, pistons press the pads due to pressure generated in the master cylinder. The pads then rub against the rotor, slowing the vehicle.
2) Drum Brakes: The working parts of a drum brake are contained inside the brake drum. The drum is attached to the hub of the wheel and revolves with it. Inside the drum are pair of curved brake shoes that are held close to the drum by retractor springs.