It does this at a much faster rate and with better control than many drivers could manage. Since initial widespread anti lock braking system working pdf in production cars, anti-lock braking systems have been improved considerably. Recent versions not only prevent wheel lock under braking, but also electronically control the front-to-rear brake bias.
The concept for ABS predates the modern systems that were introduced in the 1950s. In 1908, for example, J. Francis introduced his ‘Slip Prevention Regulator for Rail Vehicles’. The flywheel is attached to a drum that runs at the same speed as the wheel. In normal braking, the drum and flywheel should spin at the same speed. However, when a wheel slows down, then the drum would do the same, leaving the flywheel spinning at a faster rate.
This causes the valve to open, allowing a small amount of brake fluid to bypass the master cylinder into a local reservoir, lowering the pressure on the cylinder and releasing the brakes. The use of the drum and flywheel meant the valve only opened when the wheel was turning. An additional benefit was the elimination of burned or burst tires. The first patented system was created by German engineer Karl Wessel in 1928. The experiments demonstrated that anti-lock brakes can be of great value to motorcycles, for which skidding is involved in a high proportion of accidents. Stopping distances were reduced in most of the tests compared with locked wheel braking, particularly on slippery surfaces, in which the improvement could be as much as 30 percent. Enfield’s technical director at the time, Tony Wilson-Jones, saw little future in the system, however, and it was not put into production by the company.
It was available for several years thereafter, functioned as intended, and proved reliable. Such cars were very rare however and very few survive today. Prelude, launched worldwide in 1982. Additional info: The general agent for Honda in Norway required all Preludes for the Norwegian market to have the ALB-system as a standard feature, making Honda Prelude to be the first car delivered in Europe with ABS as a standard feature. The Norwegian general agent also included sun roof and other options to be standard equipment in Norway, adding more luxury to the Honda brand. However, the Norwegian tax system made the well-equipped car very expensive, and the sales suffered from high cost.
From 1984 the ALB-system, as well as the other optional features from Honda, was no longer a standard feature in Norway. European market with a Teves electronic system throughout the range as standard. Award in 1986, with very favourable praise from motoring journalists. After this success Ford began research into Anti-Lock systems for the rest of their range, which encouraged other manufacturers to follow suit. Introduced the FJ1200 model with optional ABS in 1991.
In 2005, Harley-Davidson began offering an ABS option on police bikes. Conversely, if the ECU detects a wheel turning significantly faster than the others, brake hydraulic pressure to the wheel is increased so the braking force is reapplied, slowing down the wheel. This process is repeated continuously and can be detected by the driver via brake pedal pulsation. Some anti-lock systems can apply or release braking pressure 15 times per second. Because of this, the wheels of cars equipped with ABS are practically impossible to lock even during panic braking in extreme conditions. The ECU is programmed to disregard differences in wheel rotative speed below a critical threshold, because when the car is turning, the two wheels towards the center of the curve turn slower than the outer two. If a fault develops in any part of the ABS, a warning light will usually be illuminated on the vehicle instrument panel, and the ABS will be disabled until the fault is rectified.
ABS is offered or comes standard on most road vehicles produced today and is the foundation for electronic stability control systems, which are rapidly increasing in popularity due to the vast reduction in price of vehicle electronics over the years. Modern electronic stability control systems are an evolution of the ABS concept. ABS that wheels on the inside of the curve should brake more than wheels on the outside, and by how much. If, when accelerating, the tire loses traction, the ABS controller can detect the situation and take suitable action so that traction is regained. More sophisticated versions of this can also control throttle levels and brakes simultaneously. A speed sensor is used to determine the acceleration or deceleration of the wheel.
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.
There is a valve in the brake line of each brake controlled by the ABS. 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. 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.
The pump 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 releases 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 pump’s status in order to provide the desired amount of pressure and reduce slipping.
If a wheel loses traction, the signal is sent to the controller. ABS modulator which actuates the braking valves on and off. There are many different variations and control algorithms for use in ABS. The controller monitors the speed sensors at all times. It is looking for decelerations in the wheel that are out of the ordinary.