Anti-lock Brakes

The emergence of the anti-lock braking system in vehicles has greatly improved the performance and safety of the automobile. Anti-lock brakes, or commonly referred to as ABS, basically allows for better overall stopping, especially on icy or slippery road surfaces.

When the brakes are applied on a ground surface that has little to no traction, the wheels tend to skid and lock up with the pressing down of the brake. Not so with the anti-locking brake system. The ABS is designed to prevent wheel locking. Allowing the wheel to continue its rotation increases the amount of traction the wheel will gain on the surface of the road.

Anti-lock braking involves several specific mechanisms which allows for better braking time, distance, and traction. One of the main facets of the ABS involves the utilization of speed sensors. The speed sensors transmit important information to the system in order to monitor the wheel rotation and the likelihood of potential locking. Speed sensors are mounted on all four tires and are monitored continuously by the ABS.

The presence of valves in the actual brake lines are vital to the anti-lock system. The valves generally are capable of operating in three separate positions. An open valve allows direct pressure to be applied to the brake. In the block position, the valve basically blocks or stops the pressure in the brake from rising. The valve also has a release position which allows for only a certain level of pressure to be sent to the brake. The release position is essential during conditions in which there is little to no traction present. The tendency to press hard on the brake typically would seize the wheels, yet with the ABS, this is eliminated due to the release and blocking mechanisms.

ABS comes equipped with a pump, which works by increasing brake fluid pressure when normal braking is needed. The pump works opposite of the valves, in that the valves decrease the amount of brake pressure, and the pump increases it.

The advanced electronics involved in an anti-lock braking system are key to its efficient operation. A computer device known as the controller operates all of the individual mechanisms such as the determination of speed through the sensors, valve control, and pump optimization. The entire ABS system is centered around the controller.

One of the main responsibilities of the ABS controller is to monitor the acceleration and deceleration of the vehicle through the sensor controls in mounted on the individual wheels. Deceleration generally occurs just prior to the wheels locking. The controller is capable of identifying the connection between the deceleraton and potential for the brakes locking. To correct the deceleration, the controller signals the valves to decrease the amount of pressure in the brake in order to avoid locking. During this entire process, the driver will feel a pulsation response in the brake peddle, signifying the ABS mechanism in action.

Anti-lock braking systems are categorized into three separate types. The first, and most efficient is referred to as the four-channel, four-sensor ABS. The four-channel system employs four speed sensors (one for each wheel), and four separate valves to regulate brake pressure. The ABS controller in this specific system monitors the highest amount of braking force capable of each individual wheel.

A three-channel, three sensor Anti-lock braking system consists of one sensor to measure the speed of both rear wheels, and one for each of the individual front wheels. This type of ABS is used mainly in four-wheel drive vehicles such as trucks and sport-utility vehicles.

The one-channel, one sensor ABS is geared toward rear-wheel drive vehicles such as pickup trucks. This system is equipped with only one brake valve to control pressure to the rear wheels, as well as one speed sensor which is located near the rear axle of the vehicle. This system is the least reliable of the three types of anti-locking systems.

Overall, the true efficiency and safety improvements that have evolved along with the anti-lock brake systems have been monumental to the auto industry. ABS is by far one of the most vital pieces of technology to come about in modern day computerized mechanics.