ANTILOCK BRAKE SYSTEM

ANTILOCK BRAKE SYSTEM

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  GUJARAT TECHNOLOGICAL UNIVERSITY L.D. COLLEGEOF ENGINEERING, AHMEDABAD.
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  M. E. (I.C. E. & AUTO.) SEMESTER – 3rd YEAR 2014 - 15. AUTOMOTIVE AERODYNAMICS & SAFETY (2731104)
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  ANTI-LOCK BRAKE SYSTEM (ABS) PreparedBy: G. A. KAPADIA (140280711009) A. H. SHUKLA (140280711016)
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  ANTI-LOCK BRAKE SYSTEM: Introduction: Wheel lockup during braking causes skidding which in turn cause a loss of traction and vehicle control  This reduces the steering ability to change direction. So the car slides out of control  With ABS system, the driver can brake hard, take the evasive action and still be in control of the vehicle in any road condition at any speed and under any load.
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  ANTI-LOCK BRAKE SYSTEM: Anti-lock braking system (ABS) is an automobile safety system that allows the wheels on a motor vehicle to maintain tractive contact with the road surface according to driver inputs while braking, preventing the wheels from locking up (ceasing rotation) and avoiding uncontrolled skidding.  ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces; however, on loose gravel or snow-covered surfaces, ABS can significantly increase braking distance, although still improving vehicle control.
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  CONCEPT OF ABS A skidding wheel (where the tire contact patch is sliding relative to the road) has less traction than a non- skidding wheel  By keeping the wheels from skidding while you slow down, anti-lock brakes benefit you in two ways:  Vehicle will stop faster, and it will be able to steer while you stop.
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  COMPARISON
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  COMPONENTS OF ABS Thereare four main components of ABS: speed sensors, valves, a pump, and a controller. 1. Speed sensors: A speed sensor is used to determine the acceleration or deceleration of the wheel. These sensors use a magnet and a coil of wire to generate a signal. The rotation of the wheel or differential induces a magnetic field around the sensor. The fluctuations of this magnetic field generate a voltage in the sensor. Since the voltage induced in the sensor is a result of the rotating wheel, this sensor can become inaccurate at slow speeds. The slower rotation of the wheel can cause inaccurate fluctuations in the magnetic field and thus cause inaccurate readings to the controller.
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  2. Valves  Thereis a valve in the brake line of each brake controlled by the ABS. On some systems, the valve has three positions:  In position one, the valve is open; pressure from the master cylinder is passed right through to the brake.  In position two, the valve blocks the line, isolating that brake from the master cylinder. This prevents the pressure from rising further should the driver push the brake pedal harder.
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  Continue…  In positionthree, the valve releases some of the pressure from the brake.  The majority of problems with the valve system occur due to clogged valves. When a valve is clogged it is unable to open, close, or change position. An inoperable valve will prevent the system from modulating the valves and controlling pressure supplied to the brakes.
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  3. Pump  Thepump in the ABS is used to restore the pressure to the hydraulic brakes after the valves have released it. A signal from the controller will release the valve at the detection of wheel slip. After a valve release the pressure supplied from the user, the pump is used to restore a desired amount of pressure to the braking system. The controller will modulate the pumps status in order to provide the desired amount of pressure and reduce slipping.
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  4. Controller  Thecontroller is an ECU type unit in the car which receives information from each individual wheel speed sensor, in turn if a wheel loses traction the signal is sent to the controller, the controller will then limit the brake force (EBD) and activate the ABS modulator which actuates the braking valves on and off.
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  ABS TYPES 1. Four-channel,four-sensor ABS 2. Three-channel, four-sensor ABS 3. Three-channel, three-sensor ABS 4. Two-channel, four sensor ABS 5. One-channel, one-sensor ABS
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  WORKING PRINCIPLE OFABS:
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  WORKING PRINCIPLE OFABS:
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  ADVANTAGES  It allowsthe driver to maintain directional stability and control over steering during braking  Safe and effective  Automatically changes the brake fluid pressure at each wheel to maintain optimum brake performance.  ABS absorbs the unwanted turbulence shock waves and modulates the pulses thus permitting the wheel to continue turning under maximum braking pressure.
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  DISADVANTAGES  It isvery costly  Maintenance cost of a car equipped with ABS is more.
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  REFERENCE:  http://en.wikipedia.org/wiki/Anti- lock_braking_system  http://www.engin.umich.edu/group/ctm/index.html How Stuff Works from the article “How Anti-Lock Brakes Work” http://www.howstuffworks.com/