ABS, or anti-lock braking system, is a safety feature that is implemented on buses, trucks, cars, motorcycles, and airplanes. It functions by preventing the wheels from locking up during braking, thereby ensuring that the vehicle maintains tractive contact with the road surface and that the driver has greater control over the vehicle.
In this reading, we’ll explore what an anti-lock braking system is, its functions, diagram, components, types, and how it works.
Let’s get started!
What Is an Anti-Lock Braking System?
An anti-lock braking system is a safety device designed for the automotive system to prevent the wheels from locking up under emergency or harsh braking conditions. Almost all modern vehicles, including four- and two-wheelers, now feature the system due to the latest safety regulations.
Additionally, an anti-lock brake system (ABS) is known to be a safety anti-skid braking system used on aircraft and vehicles such as cars, motorcycles, buses, and trucks. The system allows the driver or rider to have control over the vehicle as the wheels are prevented from locking up during braking. Anti-lock braking also maintains tractive contact with the road surface.
Functions Of Anti-Lock Braking System
The Anti-Lock Braking System (ABS) plays a crucial role in vehicle safety, helping maintain control during emergency braking situations. Here are the primary functions of ABS:
- An anti-lock braking system enhances vehicle control, even when encountering obstacles.
- It features a controller that monitors the speed sensors at all times. It checks for deceleration in the wheel that is out of the ordinary. This occurs right before the wheel locks up, making a rapid deceleration. If the checking never occurs, the wheel stops much quicker than it could.
- This eliminates the need to manually pump the brakes while driving on a low-traction surface or a slippery surface. This allows for efficient steering in most emergency braking conditions.
- Drivers will experience pulsing in the brake pedal when the system is in operation due to the opening and closing of the valves. The pulsing indicates to the driver that the ABS is working.
- The ABS controller is a program to know the rapid deceleration of a car is impossible. This means when a rapid deceleration happens, the wheel is about to slip, so it reduces the pressure to take that brake until it experiences an acceleration. This is when it increases the pressure until its deceleration occurs
Diagram Of An Anti-Lock Braking System
Related: What Is A Braking System? Its Parts, Types, And How It WorkWorks
Components Of Anti-Lock Braking System
The ABS consists of several components that work together to modulate brake pressure and prevent wheel lock-up. Here are the key components of an ABS:
Speed Sensors
A speed sensor is also known as an encoder, as it helps to determine the acceleration or deceleration of the wheel. The component works with a magnet and a hall effect sensor, or a toothed wheel and an electromagnetic coil to produce a signal.
As the wheel rotates, it induces a magnetic field around the sensor, which generates a voltage in the sensor as the magnetic field fluctuates around it. The sensor becomes inaccurate at slow speeds because the slower rotation of the wheel can cause incorrect fluctuations in the magnetic field. This causes inaccurate readings to the controller.
Valves
The anti-lock brake system contains a valve as its component. There are typically three positions on some systems, and ABS itself controls it. In position one, the valve opens, allowing pressure from the master cylinder to pass right through to the brake.
In position two, the valve blocks the line, separating the brake from the master cylinder. If this happens, the pressure is prevented from rising further. In the third position, the valve releases some pressure from the brake. A clogged valve is a common problem that occurs in the anti-lock braking system.
Controller
The controller serves as an ECU device as it receives information from each wheel speed sensor. A signal is sent to the controller if the wheel loses traction. The controller will limit the brake force (EBD) and then activate the ABS modulator, which actuates the braking valves on and off.
Pump
The function of the pump is to restore the pressure to the hydraulic brakes after the valves release it. A controller shows a signal that releases the valve when a slip is detected in the wheel. As soon as a valve releases the pressure that the driver has applied, the pump restores the desired amount of pressure to the braking system. The controller will then modulate the pump’s condition to provide the desired amount of pressure and reduce slipping.
Types Of Anti-Lock Braking System
Anti-lock braking systems work with various schemes depending on the types of brake employed. Below are the types of anti-lock braking systems in automotive vehicles:
Four-Channel, Four-Sensor ABS
These types of ABS contain a speed sensor on the four wheels and a separate valve for all four wheels. This setup allows the controller to monitor each wheel individually, ensuring the maximum braking force is achieved.
Three-Channel, Four-Sensor ABS
This anti-lock braking system setup contains a speed sensor on all four wheels and a separate valve for each of the front wheels. One valve is employed for both wheels at the rear. These types of ABS are used on older vehicles with four wheels.
Three-Channel, Three-Sensor ABS
This system carries a speed sensor and a valve for each of the front wheels. The rear wheels feature one valve and one sensor for both wheels. This scheme is commonly found on pickup trucks with four-wheel ABS. In this system, individual control is provided on the front wheels so that maximum braking force can be obtained.
The rear wheels have to start to lock up before the ABS will activate on the rear. However, the wheels are monitored together. In these types of anti-lock brake systems, there is a possibility that one of the rear wheels will lock during a stop. This will reduce brake effectiveness. Well, the system is easy to identify since there are no individual speed sensors for the rear wheels.
Two-Channel, Four-Sensor ABS
This system is commonly found in passenger cars that exist from the late ’80s through the mid-90s. It works with a speed sensor at each wheel and one control valve for each of the front and rear wheels as a pair. The control module pulses the valve for both wheels on that end of the car if the speed sensor in any individual wheel detects any lock-up.
One-Channel, One-Sensor ABS
This system is commonly used on pickup trucks, vans, and SUVs as it contains one valve that controls both rear wheels. It also has a one-speed sensor, located in the rear axle. Its working is just like the rear end of a three-channel system.
The rear wheels are monitored together, and they have to lock up before the ABS actuates. In this system, there is also a possibility that one of the rear wheels will lock, which reduces brake effectiveness. The system is easy to identify, as there are no individual speed sensors for any of the wheels.
Related: What Is A Hydraulic Braking System? Its Diagram & How It Works
How An Anti-Lock Braking System Works
In a car with ABS, each wheel hub has a sensor that measures the speed at which each wheel spins as well as the rate of acceleration and deceleration. It is frequently a component of the vehicle’s Electronic Stability Control (ESC) system. You cannot have ESC without anti-lock brakes; however, not all automobiles with ABS have this technology.
ABS detects whether the wheels are likely to lock when the driver brakes abruptly. After that, it applies the ideal brake pressure by quickly lowering and raising it several times per second. This prevents the wheels from locking up as the vehicle slows down. The car is less likely to skid, and the driver has more control over the steering.
Advantages
The Anti-Lock Braking System (ABS) offers several advantages that enhance vehicle safety and control. Here are the main benefits of ABS:
- ABS prevents lockups and skidding, even in slippery conditions like stopping on ice, oily, or wet roads. The system is assured to save a life in such a condition, giving the driver perfect control of the vehicle.
- Due to the effectiveness of the device, it’s now mandatory by law for all vehicles to feature them. This makes it easy for drivers to purchase devices that carry the system at low insurance costs.
- Modern ABS is designed to have a traction control system, which allows all-wheel traction on the road. This makes it easy for manufacturers to do both features in the factory.
- Cars or trucks feature anti-lock brake systems and have higher resale value as the system continues to rise.
Disadvantages
While the Anti-Lock Braking System (ABS) provides numerous benefits, it also has some potential disadvantages:
- The system is delicate. It’s easy for the system to cause problems with the brakes, such as disorientation of the ABS, where the vehicle is caused to shudder because of the brake sensors.
- An anti-lock brake can be expensive to maintain depending on the car model. Sensors on each wheel can cost much to fix when they develop a fault. This is the reason why most people don’t have ABS on their vehicles.
- ABS ensures ideal braking in slippery conditions, but some users complain of inconsistent stop time. That is, their ABS lengthens the stopping distances under normal circumstances. The system’s error is to blame for this.