Brake-By-Wire
Brake-By-Wire is a part of the drive-by-wire technology that has been taking the automotive industry by storm in recent times. The core concept of every drive-by-wire system is identical: replace the mechanical connections and linkages with electronic connections in order to make the assemblies lighter, simpler, and easier to integrate. Brake-by-wire is no different, although it has room for many different systems and features to be implemented through integration with the brake system, such as automatic emergency braking (AEB), electronic stability control, and traction control.
Any Brake-By-Wire system consists of a brake control unit (BCU), brake pedal position sensor, and electromechanical or electrohydraulic actuators, instead of the traditional hydraulic system. Thus, it takes the mechanical connection between the brake calipers and pedals out of the equation, and the braking pressure is applied through electronic connections.
How does a Brake-by-wire system work?
The pedal position sensor is responsible for communicating two pieces of information to the brake control unit – the extent to which the pedal is actuated, and the urgency with which it is actuated. Using this information, the brake control unit calculates the amount of braking force that needs to be applied to the wheels. By correlating the braking force with the amount of pressure to be applied, the control unit sends the appropriate signals to the actuator, which then takes care of the requested deceleration.
Brake-By-Wire 2023| Dorleco
The brake-by-wire also allows the brake feel to be tailored to certain driving modes, which can be very useful in terms of human-vehicle interface. While most systems follow a similar architecture up to this point, the actuation of the caliper can vary based on what type of Brake-By-Wire system is being used.
Redundancy in designing Brake-By-Wire systems
Brake-By-Wire systems are mainly categorized based on whether or not the pressure is applied to the caliper by using a hydraulic circuit. The connection between the pedal and calipers is electronic in all cases, but purely electrical actuation of the caliper (“dry” brake-by-wire) hasn’t been completely accepted by the industry yet.
The cause for this is that there are doubts regarding the reliability of purely electric actuation, especially about whether this kind of system will be able to apply the accurate amount of pressure to the calipers or not.
Brake-By-Wire 2023| DorlecoSource: https://www.mdpi.com/2076-0825/9/1/15
Hence, a hybrid system is used, where one of the axles contains a partial hydraulic circuit, thus providing redundancy to the system. The electrical signal is sent to the electrohydraulic actuators, which convert the electrical energy into hydraulic pressure to apply to the calipers.
If, at some point, the control unit realizes that something is wrong, a valve opens up bypassing all electronics, and a conventional hydraulic system starts functioning. This helps in providing redundancy and increasing the safety of the entire system.
Safety Features for Brake-By-Wire Systems
Brake-by-wire allows for ease of integration of the brakes system with other safety features, thus helping in making the drive much safer, while also enabling automakers to move along on the path toward vehicle autonomy.
These features include:
Traction control
Traction control essentially consists of measuring the wheelspin to get an idea of the accelerative traction available. This traction is then controlled by using anti-lock braking to apply extra braking pressure on a wheel spinning too fast or using the electronic throttle control to limit the power sent to that wheel.
An electronically-controlled braking system can thus be easily integrated with a traction control system, as it allows for varying the amount of pressure acting on different wheels.
Electronic stability control (ESC)
One of the most integral safety features used in “smart” vehicles nowadays is electronic stability control. It is essentially a traction control system along with additional electronic sensors, a more powerful processor, and a few extra algorithms.
On activating this system, the control unit governing the vehicle motion ensures that there is no loss in stability of the car while executing specific maneuvers. This includes the prevention of oversteer and understeer, which is achieved by varying the amount of braking force being sent to either of the wheels on the same axles, thus helping in controlling the vehicle in a better way.
Sending a variable amount of braking force to the right and left wheels is easier to achieve through an electronically-controlled braking system than a mechanically-controlled one. Hence, the Brake-By-Wire system can be easily integrated with ECS.
Automatic Emergency Braking (AEB)
Active safety features are being integrated into modern vehicles, and the automatic emergency braking system is one of the most important ones of these. It keeps monitoring the distance between any potential obstacle and the host vehicle and can stop the car completely in an emergency.
Most AEB systems consist of two stages – partial braking and complete braking. Partial braking is often accompanied by a Forward Collision Warning (FCW) system, which alerts the driver and gives him/her a chance to take control of the vehicle.
If the vehicle still doesn’t slow down sufficiently, the AEB system activates complete braking and tries to avoid or mitigate the effect of a collision in the worst-case scenario. Since this system requires a quicker response than a normal braking maneuver, electronic control is better suited than mechanical control.
Brake-By-Wire Controls Development at Dorleco:
Thus, a brake-by-wire system can allow for the integration of several safety features. Yes, the industry hasn’t completely accepted the purely electrical brake-by-wire system yet owing to the fatal consequences of a system failure,
but the hybrid approach will definitely help automakers implement this system and improve the overall safety and response of the vehicles of the future. At Dorleco, we are working on developing control software for brake-by-wire systems, and integrating and testing such systems on the test bench as well as prototype vehicles.
If you wish to discuss possible collaborations regarding electronically-controlled braking systems, write to info@dorleco.com.