ABS – Function, Design & Working ABS types Recent Advancements Effectiveness & Limitations Testing & Validation Job of the Driver Closing Remarks To maintain the stability & steer-ability of the vehicle while the wheels are impending lock or skid in varying road conditions during braking. To maneuver in your intended direction during “panic-stop” situation. To stop the vehicle with minimum stopping distance. Consisted of Mechanical components only-Drum, Flywheel. Relative angular speed difference between Drum & Flywheel causes some drop in main hydraulic line & thereby reducing brake pressure in the adequate amount. COMPONENTS Speed Sensors-The anti-lock braking system needs some way of knowing when a wheel is about to lock up. The speed sensors, which are located at each wheel, or in some cases in the differential, provide this information. Pump-Since the valve is able to release pressure from the brakes, there has to be some way to put that pressure back. That is what the pump does; when a valve reduces the pressure in a line, the pump is there to get the pressure back up. Valves-There is a valve in the brake line of each brake controlled by the ABS. On some systems, the valve has three positions: a. In position one, the valve is open; pressure from the master cylinder is passed right through to the brake. b. 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. c. In position three, the valve releases some of the pressure from the brake. Controller-The controller is a computer in the car. It watches the speed sensors and controls the valves. Operation -Wheel speed sensor (A) senses the abnormal spinning of the wheel . -Signal(input strength) is sent to the ECU (B). -ECU processes it & communicates with HCU (C) to increase or decrease the brake pressure Tin the brake line (D) to the affected wheel. INPUT TO ABS PROCESSING OUTPUT-OPTIMUM BRAKING PRESSURE ABS – Function, Design & Working. ABS types. Recent Advancements. Effectiveness & Limitations. Testing & Validation. Job of the Driver. Closing Remarks. Four-channel, four-sensor ABS-This is the best scheme. There is a speed sensor on all four wheels and a separate valve for all four wheels. With this setup, the controller monitors each wheel individually to make sure it is achieving maximum braking force. Three-channel, three-sensor ABS-This scheme, commonly found on pickup trucks with four-wheel ABS, has a speed sensor and a valve for each of the front wheels, with one valve and one sensor for both rear wheels. The speed sensor for the rear wheels is located in the rear axle. One-channel, one-sensor ABS-This system is commonly found on pickup trucks with rear- wheel ABS. It has one valve, which controls both rear wheels, and one speed sensor, located in the rear axle. ABS – Function, Design & Working. ABS types. Recent Advancements. Effectiveness & Limitations. Testing & Validation. Job of the Driver. Closing Remarks. Function-The job of the EBD as a subsystem of the ABS system is to control the effective adhesion utilization by the rear wheels & it automatically varies the amount of force applied to each of a vehicle's brakes, based on road conditions, speed, loading/weight, etc. The pressure of the rear wheels is approximated to the ideal brake force distribution in a partial braking. EBD can apply more or less braking pressure to each wheel in order to maximize stopping power whilst maintaining vehicular control. FUNCTION- To detect loss of steering control, & automatically apply the brakes to help "steer" the vehicle where the driver intends to go. It works always with ABS. Consists of two more sensors-Steering wheel sensor & Yaw sensor.During normal driving, ESC works in the background and continuously monitors steering and vehicle direction. When there is a condition of under-steer or over-steer, the asymmetrical braking force is applied on either inner rear (to counter understeer) or outer rear wheel (to counter oversteer) which helps the vehicle to take a turn in a controlled manner & to its intended direction. FUNCTION- To prevent loss of traction of the driven road wheels, and therefore maintain the control of the vehicle when excessive throttle is applied by the driver (rapid acceleration) and the condition of the road surface (due to varying factors) is unable to cope with the torque applied. The intervention can consist of one or more of the following: Retard or suppress the spark to one or more cylinders. Reduce fuel supply to one or more cylinders. Brake one or more wheels. Close the throttle. In turbo-charged vehicles, the boost control solenoid can be actuated to reduce boost and therefore engine power. ABS – Function, Design & Working ABS types Recent Advancements Effectiveness & Limitations Testing & Validation Job of the Driver Closing Remarks Reduces the risk of multiple vehicle crashes by 18 percent, Reduces the risk of run-off-road crashes by 35 percent. On high-traction surfaces such as bitumen, or concrete, ABS reduces stopping distances. Better than Threshold braking. Reduces chances of skid & hence maintains the stability & steer-ability. Reduces wear & tear of tires. ABS fails to function when all wheels get locked during braking. Drivers of vehicles equipped with ABS tend to be careless or overconfident (psychological influence). ABS – Function, Design & Working ABS types Recent Advancements Effectiveness & Limitations Testing & Validation Job of the Driver Closing Remarks Stability & Steer-ability. Full braking on a curve & swerving. Stopping distance. More control on varying road conditions. ABS – Function, Design & Working ABS types Recent Advancements Effectiveness & Limitations Testing & Validation Job of the Driver Closing Remarks In order for ABS to Function effectively, driver should press the brake pedal as hard as possible. Do not put off your feet from the pedal if you sense “pulsing”(-it indicates that ABS is working). Driver should normally steer the vehicle to its intended direction. Don't release the pedal until you have safely stopped. ABS – Function, Design & Working ABS types Recent Advancements Effectiveness & Limitations Testing & Validation Job of the Driver Closing Remarks Today ABS is a utmost necessary advanced safety feature in almost any automobile. EBD, ESC & TCS assist ABS depending on their specific capabilities and functions. Even an alert skilled driver would find it difficult without ABS to match the performance of vehicle with ABS. Even if your vehicle has ABS, Be attentive while driving.