Recommended
More Related Content
What's hot
What's hot (20)
Similar to About abs
Similar to About abs (20)
Recently uploaded
Recently uploaded (20)
About abs
- 1. Presenter: Nguyen Van Long Lecturer : Tran Quoc Long
- 2. Content Conclusion Principles for ABS Operation ABS Components Anti-Lock Brake Types Overview Design Challenges
- 3. Overview ABS is an abbreviation for Anti- lock Braking System. It was designed to help the driver maintain some steering ability and avoid skidding while braking. What is it?
- 4. Overview 1936: German company Bosch is awarded a patent for an “Apparatus for preventing lock-braking of wheels in a motor vehicle”. 1936-: Bosch and Mercedes-Benz partner - R&D into ABS. 1972: WABCO partners with Mercedes-Benz developing first ABS for trucks. 1978: First production-line installation of ABS into Mercedes and BMW vehicles. 1981: 100,000 Bosch ABS installed. 1985: First ABS installed on US vehicles. History of ABS
- 5. Overview 1986: 1M Bosch ABS installed. 1987: Traction control - in conjunction with ABS - used on passenger vehicles. 1989: ABS hydraulic unit combined with standard hydraulic brake unit 1992: 10M Bosch ABS installed. 1995: Electronic Stability - in conjunction with ABS and TCS - for passenger cars. 1999: 50M Bosch ABS installed. 2000: 6 of 10 new cars on the road are ABS equipped. 2003: 100M Bosch ABS installed. History of ABS
- 6. Anti-Lock Brake Types Depending on the ABS application, there are several typical layouts.
- 8. ABS Components ABS Speed Sensors A speed sensor is used to determine the acceleration or deceleration of the wheel.
- 9. ABS Components Solenoid Valve The valves modulate the brake pressure up to 20 times per second, effectively realizing the ideal tire slip percentage.
- 10. ABS Components The valve has three positions: Position 1 : Increase pressure Position 2: Hold pressure steady : in this mode of operation both solenoids are closed and no additional fluid is allowed to flow to brake calipers. Position 3 : Decrease pressure: in this mode the pressure increase solenoid is closed. The Vent solenoid opens allowing fluid to vent into an accumulator chamber Solenoid Valve
- 11. ABS Components ABS Pumps The pump in the ABS is used to restore the pressure to the hydraulic brakes after the valves have released it.
- 12. ABS Components ABS Controller The brains of the system. ABS Controllers are a computer that reads the inputs and then controls the system to keep the wheels from locking up and skidding.
- 13. Principles for ABS Operation ABS Operating Diagram
- 14. Principles for ABS Operation
- 15. Principles for ABS Operation ABS block diagram
- 16. Design Challenges ABS system can be designed for a variety of applications such as aircraft, cars, trucks, motorcycles, bicycles ... Each object has a different operating condition, so the design must be optimized for each of these objects Object uses
- 17. Design Challenges Theoretical basis (A)Slip ratio (B) Coefficient of friction between tire and road surface (1) Icy road (2) Asphalt-paved road (3) Control range by ABS The best braking action occurs at between 10-20%. If vehicle speed and wheel speed is the same wheel slippage is 0% A lock-up wheel will have a wheel slippage of 100% Slip ratio= (Vehicle speed - wheel speed ) / vehicle speed × 100%
- 18. Design Challenges Control methods ABS Research Classical Control Optimal control Nonlinear control Robust control Adaptive control Intelligen t control Sampling of ABS control Many different control methods for ABS systems have been developed. These methods differ in their theoretical basis and performance under the changes of road conditions.
- 19. Conclusion • An ABS typically consists of: • Up to 4 wheel speed sensors • An ABS ECU • A Brake Master Cylinder, with accompanying Hydraulic Modulator Unit and Solenoid Valves • The vehicle’s physical brakes • An ABS is designed to modulate braking pressure to attain the peak coefficient of kinetic friction between the tire and the road, and to avoid total wheel lockup. • An ABS, under hard braking conditions, is designed to reduce stopping distances under most conditions, while maintaining vehicle stability and steerability.
Editor's Notes
- Hello every body, today I am talk about ABS system, that device is used popular in cars today. The presentation has the following content:
- Anti-Lock Braking Systems (ABS) are designed to maintain driver control and stability of the car during emergency braking. Locked wheels will slow a car down but will not provide steering ability. ABS allows maximum braking to be applied while retaining the ability to 'steer out of trouble‘ . The operation of ABS can slightly reduce stopping distance in some cases like on wet road surfaces, but it can increase the stopping distance in others, as may be the case in deep snow or gravel.
- The ABS system was invented in 1936. In the process of development it was added to complement and improve by many company. Today the abs system is very intelligent and is used on a wide variety of vehicles at reasonable prices.
- Anti-lock braking systems use different schemes depending on the type of brakes in use. They can be differentiated by the number of channels: that is, how many valves that are individually controlled—and the number of speed sensors. 1) Four-channel, four-sensor ABSThere 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.2) Three-channel, four-sensor ABSThere is a speed sensor on all four wheels and a separate valve for each of the front wheels, but only one valve for both of the rear wheels. Older vehicles with four-wheel ABS usually use this type.3) Three-channel, three-sensor ABSThis 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. This system provides individual control of the front wheels, so they can both achieve maximum braking force. The rear wheels, however, are monitored together; they both have to start to lock up before the ABS will activate on the rear. With this system, it is possible that one of the rear wheels will lock during a stop, reducing brake effectiveness. This system is easy to identify, as there are no individual speed sensors for the rear wheels.4) Two-channel, four sensor ABSThis system, commonly found on passenger cars from the late '80s through the mid 1990s, uses a speed sensor at each wheel, with one control valve each for the front and rear wheels as a pair. If the speed sensor detects lock up at any individual wheel, the control module pulses the valve for both wheels on that end of the car.5) One-channel, one-sensor ABSThis system is commonly found on pickup trucks, SUVs, and vans with rear-wheel ABS. It has one valve, which controls both rear wheels, and one speed sensor, located in the rear axle. This system operates the same as the rear end of a three-channel system. The rear wheels are monitored together and they both have to start to lock up before the ABS kicks in. In this system it is also possible that one of the rear wheels will lock, reducing brake effectiveness. This system is also easy to identify, as there are no individual speed sensors for any of the wheels.
- There are four main components of ABS: wheel speed sensors, valves, a pump, and a controller.
- 1. Speed sensors are comprised of a magnet ('mægnit) wrapped(ræpə) in a coil and a toothed sensor ring. An electrical field given off by the contact between the magnet and the toothed ring creates a AC voltage. 2. The voltage frequency is directly proportional to the wheel's rotational speed. 3. It monitors the rotational speed of the wheel and transmits this data to the ABS control module.
- ; some system have separate valves for each wheel with a modulator to control them. Other systems they are combined. In either case they work with the controller and the pump to add or release pressure from the individual wheels brakes to control the braking.
- There is 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. In position three, the valve releases some of the pressure from the brake.
- 1. It receives operating signals from the ECU to apply or release the brakes under ABS conditions. 2. It executes the commands using three solenoid valves connected in series with the master cylinder and the brake circuits- one valve for each front wheel hydraulic circuit, and one for both of the rear wheels. Thus brakes can be actuated by controlling hydraulic pressure.
- 1. It receives signals from the sensors in the circuit and controls the brake pressure at the road wheels according to the data analysed by the Unit. 2. ECU assists the vehicle operator to prevent wheel lockup by regulating the wheel slip.
- This is a video explaining the operation of the ABS system Basically/'beisikəli/, there are sensors at each of the four wheels (or in the case of the less sophisticated/sə'fistikeitid/ three-channel system, one on each of the fronts and only one for the pair of rears). These sensors watch the rotation of the wheels. When any one of the wheels stops rotating due to too much brake application, the sensors tell the car's computer, which then releases some of the brake line pressure that you've applied - allowing the wheel to turn again. Then, just as fast as it released the pressure, the computer allows the pressure to be applied again - which stops the rotation of the wheel again. Then it releases it again. And so on. With most ABS, this releasing and re-application - or pulsing - of the brake pressure happens 20 or more times per second. Practically speaking, this keeps the wheel just at the limit - the threshold - before locking up and skidding. ABS prevents you from ever locking up the brakes and skidding - no matter how hard you apply the brakes. Obviously, this is going to mean much more steering control. With ABS, all you have to do in an emergency is quickly squeeze the brake pedal as hard as you can and hold it there. And when I say hard, I mean HARD. Let the system do the finesse work for you. This may not be as easy as it sounds. After years of being told (and practising) not to press too hard on the brake pedal, this may not feel very natural.
- - If a wheel-speed sensor signals a lock up - the ECU sends a current to the hydraulic unit. This energizes the solenoid valve. The action of the valve isolates the brake circuit from the master cylinder. This stops the braking pressure at that wheel from rising, and keeps it constant. It allows wheel velocity to increase and slip to decrease. - When the velocity increases, ECU re-applies the brake pressure to restrict the wheel slip to a particular value. - Hydraulic control unit controls the brake pressure in each wheel cylinder based on the inputs from the system sensor. This in result controls the wheel speed.
- challenge /'tʃælindʤ/ mathematical /,mæθi'mætikəl/ relationship between braking coefficient and wheel slip
- ABS control is highly nonlinear control problem due to the complicated relationship between its components and parameters. The research that has been carried out in ABS control systems covers a broad range of issues and challenges. Many different control methods for ABS have been developed and research on improved control methods is continuing. Most of these approaches require system models, and some of them cannot achieve satisfactory performance under the changes of various road conditions. While soft computing methods like Fuzzy control doesn’t need a precise model. A brief idea of how soft computing is employed in ABS control is given.
- You have to understand that ABS does not raise the traction limits of your vehicle. It only helps you stay within the limits. Period. So, don't get caught up in believing that ABS will allow you to drive any faster, brake later or go around a corner any faster - or allow you to safely follow any closer.