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The SBC is an innovative electronically controlled braking system that Mercedes-Benz will install in future passenger cars. In line with the ABS, ASR, ESP and Brake Assist systems created by Mercedes-Benz, this system will become a new milestone in improving car driving safety.
SBC uses electronic pulses to transmit the driver's braking command to a microprocessor, which synchronously processes various sensor signals and calculates the optimal braking force for each wheel based on the specific driving conditions. In this way, when braking on a curve or slippery road, SBC can provide better active safety than traditional braking systems. The high-pressure energy storage and electronically controlled valve device of the SBC system ensure that the maximum brake pressure takes effect faster. In addition, the system provides additional functions that reduce the driver's operating intensity during driving. For example, the traffic congestion assistance function: in stop-and-go traffic conditions, the car can automatically brake when the driver releases the accelerator pedal. Its soft stop function allows the car to stop particularly softly and smoothly in city traffic.
So far, cars still rely purely on mechanical or partially hydraulic assistance to achieve various functions. With the widespread application of mechatronics in the automotive industry, in the future, various functions of automobiles will be realized by high-performance microprocessors and controllable electronic actuators, which will replace traditional mechanical components and further improve the safety and comfort of modern passenger cars. For example, the Active Body Control (ABC) launched by Mercedes-Benz in 1999 is one of the examples of the application of mechatronics in automobiles. This electronically controlled suspension system enables the car to reach the optimal state immediately when starting, braking or turning. Mercedes-Benz applied this system on its flagship CL model under the name of "Active Body Control (ABC)". It marks the arrival of a new era in suspension technology.
The electronically controlled brake system with integrated measurement and control will appear with the advent of the electronically controlled suspension system. Mercedes-Benz and BOSCH have begun to cooperate on this development project and have mass-produced it under the name of "Integrated Braking Control System (or SBC)".
The integrated braking control system transforms the traditional hydraulic brake system into a more powerful mechatronic system. Its microprocessor is integrated into the vehicle's data network and can process information from different electronic control devices. In this way, electronic pulses and sensor signals can be quickly converted into brake signals, giving the driver a significant sense of security and comfort.
SBC system operation diagram
Brake pedal: electronic type instead of vacuum type
The working principle of the current brake is: the driver steps on the brake pedal and pushes the piston connecting rod connected to the brake pressure regulator and the brake master cylinder. The brake master cylinder will form a corresponding pressure on the braking route according to the size of the pedal force. Under the interaction of mechanical and hydraulic forces, the brake caliper is pushed against the brake disc through the wheel side brake cylinder.
In the future integrated measurement and control electronic control braking system, electronic components will replace the mechanical components used in large quantities in the current braking system, and the pressure regulator will no longer be needed. Instead, sensors will be used to measure the pressure in the brake master cylinder and the speed of the brake pedal movement, and these data will be transmitted to the SBC processor in the form of electronic pulses.
In order to give the driver a similar braking feeling, engineers have developed a special simulator, which is connected to the front and rear brake master cylinders to push the brake pedal with spring force and hydraulic force. In other words: during the braking process, the actuator is completely disconnected from the rest of the system and is only responsible for recording any braking commands issued. Only in the event of a serious error or a problem in the 12V vehicle battery does the SBC automatically use the front and rear master cylinders and quickly establish a hydraulic connection between the brake pedal and the front wheel brakes to ensure safe deceleration of the vehicle.
Control unit: pressure regulator for each wheel
The central control unit is the heart of the electronic hydraulic brake. This is where mechanics and electronics interact to their greatest advantage - microprocessors, software, sensors, valves and electric pumps work together to achieve efficient dynamic brake management:
In addition to receiving information about the movement of the brake pedal, the SBC processor also receives sensor signals from other electronic assistance systems. For example, the anti-lock braking system (ABS) provides information about the wheel speed; EPS receives relevant data from sensors such as steering angle, rotation rate, lateral acceleration, etc. The powertrain control unit finally uses the data channel to communicate the current driving status. The result of this highly complex calculation will generate a rapid braking command to ensure the best deceleration and driving stability adapted to the specific driving situation. Because the SBC calculates the required braking force for each wheel separately, the braking system can control the brakes very accurately.
The high-pressure accumulator contains brake fluid that can enter the brake system at a pressure of 14 to 16 kPa. The SBC processor regulates this pressure and controls the electric pump connected to the accumulator. This ensures a shorter response time than a conventional brake system. Another advantage is that full braking force is available even when the engine is turned off.
The hydraulic system mainly consists of four so-called "wheel pressure regulators". They generate the required brake pressure and transmit it to the brakes. In this way, each wheel can be decelerated smoothly in response to the constraint instructions of the microprocessor to achieve the best driving stability and optimal deceleration. These processes are monitored by pressure sensors installed in the wheel pressure regulators. Emergency braking: braking distance can be reduced by 3%
The most important performance feature of the SBC system is its extremely dynamic characteristics during the pressure build-up process and the precise monitoring of the driver and vehicle movements using highly sensitive sensors. In emergency braking, for example, SBC recognizes the driver's movements on the brake pedal via the accelerator as a clue to emergency braking and responds quickly: With the help of the high-pressure accumulator, the SBC system increases the pressure in the brake line and quickly presses the brake calipers against the brake discs, allowing them to quickly catch the moment the driver presses the brake pedal. The result: a sports car equipped with SBC brakes at a speed of 120 km/h with a braking distance reduced by about 3% compared to a model with a conventional brake system.
The performance of the brake assist system has also been further improved with the help of electro-hydraulic technology. When the system executes the braking command and realizes an automatic emergency stop, the rapidly generated brake pressure and the automatic preloading of the wheel brakes shorten the braking distance.
Driving stability: precise brake pulses guarantee excellent performance of EPS
SBC is not only valuable in emergency braking, but also in other critical situations. For example, in dangerous situations of sudden turns, the SBC system interacts with the Electronic Stability Program (ESP) to ensure the safety of the vehicle during sudden turns by sending precise braking pulses to each wheel and/or reducing the engine speed. SBC shows its powerful dynamics and precision here. It is precisely because of the faster and more precise braking pulses from the SBC high-pressure accumulator that ESP can stabilize the vehicle in a timely and smooth manner when it is about to leave the driving track.
ESP and various technologies in conjunction with
the test show that with the participation of SBC, ESP can work more effectively through fast and precise braking pulses and can significantly reduce the sudden turns of the car. At the same time, the steering pressure of the driver is reduced. With SBC and EPS, the driver can reduce a lot of difficulties when controlling the car on the move. Braking on bends: Variable brake force distribution for greater safety
When braking on bends, SBC offers greater safety than conventional brake systems. Variable brake force distribution has the unique advantage of positively influencing the car's cornering behavior.
Conventional brake systems usually apply equal brake pressure to the inner and outer wheels, but SBC offers the possibility of distributing the brake force appropriately according to the situation. Therefore, the system automatically increases the brake pressure on the outer wheel. This allows a greater braking force to be transmitted because the outer wheel is subject to a higher vertical load. At the same time, the braking force on the inner wheel is reduced to generate the higher turning forces required in bends. The result is more stable braking behavior and optimal deceleration values.
Despite the innovative integrated brake control system, the design engineers still adhered to the principle of variable brake force control for the front and rear axles. They designed the system to work in such a way that when slowing down from high speeds, most of the braking force continues to act on the front axle, which avoids potentially dangerous brake locking of the rear axle. At low speeds or during partial braking, the system automatically increases the brake force distributed to the rear axle to improve the response of the braking system and to achieve more even wear of the front and rear brake pads.
The new SL-Class series equipped with SBC in the cornering
comfort: no brake pedal vibration when ABS is in operation
The separate design of the SBC pedal in the braking system and the use of mechatronic balanced pressure control improve the comfort of braking, especially when decelerating sharply or when the ABS system is in operation. The brake pedal vibration that is common in ABS operation will no longer occur. Studies in driving simulators have shown that almost two-thirds of drivers begin to feel shocked when ABS is in operation: they dare not increase the braking force, and even take their feet off the brake pedal for a while, which will increase the braking distance of their car. Experiments in driving simulators have shown that on ice and snow covered roads, when the vehicle brakes at a speed of 60km/h, ABS will increase the braking distance by an average of 2.10m.
Additional function of SBC: Support system to reduce driving fatigue
The integrated brake control system has additional advantages in daily driving. For example, it is particularly effective on slippery roads, decelerating at traffic lights, in traffic jams or starting uphill.
The function of SBC is called soft stop. Due to the high-precision pressure control of mechatronics, the vehicle can stop gently and smoothly when it decelerates frequently at traffic lights.
On slippery roads, the system generates short brake pulses at regular intervals to ensure that the water film on the brake discs is dried and SBC works at its best. This automatic brake disc drying function is activated at regular intervals when the car's windshield wipers are working. The driver does not even feel these ultra-precise brake pulses.
The SBC system also has a function called Traffic Jam Assist. It can be activated by the cruise control lever when the car is stationary. The advantage is that in stop-and-go traffic, the driver only needs to control the accelerator pedal. As soon as the right foot leaves the accelerator pedal, SBC slows
the car down and stops it at a steady speed. Traffic Jam Assist can continue to work up to a speed of 60 km/h, but it is automatically cut off at higher speeds.
When driving on a slope, SBC's start-off assist function prevents the car from rolling backwards or forwards. The driver only needs to press the brake pedal quickly and sharply to activate the start-off assist function. If the driver accelerates, the start-off assist function releases the brakes to enable the car to move smoothly.
The future: SBC paves the way for automated navigation systems
The advent of electronics in braking systems offers engineers new and promising opportunities that extend beyond improving the safety and comfort of cars. With SBC, they have taken a major step towards their long-standing goal of enabling the car of the future to navigate itself along the road with the help of cameras, short-range radar and advanced remote-control navigation systems.
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