31-07-2014, 11:10 AM
SENSOTRANICS BRAKING CONTROL
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ABSTRACT
Braking is one of the basic needs of an automobile where the safety of a person is more stressed. Braking is the method of slowing down and bringing the vehicle to rest at shortest distance. There are many braking systems in practice where the Sensotronic braking control systems shortly known as SBC has many features that makes it more stable in it class. With Sensotronic Brake Control, electric impulses are used to pass the driver's braking commands onto a microcomputer which processes various sensor signals simultaneously and, depending on the particular driving situation, calculates the optimum brake pressure for each wheel. As a result, SBC offers even greater active safety than Conventional brake systems. The central control unit under the bonnet is the centerpiece of the Electro hydraulic brake. This is where the interdisciplinary interaction of mechanics and Electronics provides its greatest benefits - the microcomputer, software, sensors, valves And electric pump work together and allow totally novel, highly dynamic brake Management. Processes are monitored by pressure sensors inside the wheel pressure Modulators. The main performance characteristics of Sensotronic Brake Control include the extremely high dynamics during pressure build-up and the exact monitoring of driver and vehicle behavior using sophisticated sensors.
INTRODUCTION
In today’s automobile field, braking takes a mighty role. Every auto industry has a separate R&D to develop the braking facility of their vehicles. Because, braking, not only saves life but also ensures a company’s standard and their product. Besides the installment of new brake systems like ABS a new braking system named SBC( Sensotronic braking control) has a lot of new features where the braking is being controlled by an microprocessor.
Sensotronic Brake Control (SBC) Mercedes-Benz's revolutionary brake-by-wire system is standard on the new E-Class. The brake pedal is connected electrically to the main brake cylinder and a powerful microprocessor feeds information to the hydraulically activated brakes using electrical pulses. A special simulator uses spring pressure and hydraulics to give pedal resistance maintaining the driver's feel for the brakes. SBC is quicker than a conventional system resulting in shorter stopping distances around three percent at 70 mph. The system is a little unnerving to begin with especially when the driver comes to a road junction in traffic, but the driver soon gets used to it and if the driver takes his foot off the accelerator. The driver will gradually come to halt with the system braking. It also apply the brake lights. It will effectively hold the car on the brakes without having to touch the brake pedal. ABS (anti-lock braking system) with BAS (brake assist) are part of the SBC system as standard
SENSOTRONIC BRAKE CONTROL
Sensotronic Brake Control (SBC) is the name given to an innovative electronically controlled brake system which will fit to future passenger car models.
With Sensotronic Brake Control, electric impulses are used to pass the driver's braking commands onto a microcomputer which processes various sensor signals simultaneously and, depending on the particular driving situation, calculates the optimum brake pressure for each wheel. As a result, SBC offers even greater active safety than conventional brake systems when braking in a corner or on a slippery surface. A high-pressure reservoir and electronically controllable valves ensure that maximum brake pressure is available much sooner. Moreover, the system offers innovative additional functions to reduce the driver's workload. These include Traffic Jam Assist, which brakes the vehicle automatically in stop-and-go traffic once the driver takes his or her foot off the accelerator. The Soft-Stop function - another first - allows particularly soft and smooth stopping in town traffic.
THE TECHNICAL ASPECTS
In present scenario when drivers hit the brake pedal, their foot moves piston rod which is linked to the brake booster and the master brake cylinder. Depending on the pedal force, the master brake cylinder builds up the appropriate amount of pressure in the brake lines which - in a tried and tested interaction of mechanics and hydraulics then presses the brake pads against the brake discs via the wheel cylinder.
FIG 3.1 LAYOUT OF SBC
By contrast, in the Mercedes-Benz Sensotronic Brake Control, a large number of mechanical components are simply replaced by electronics. The brake booster will not be needed in future speed with which the brake pedal is operated, and pass these data to the SBC computer in the form of electric impulses. To provide the driver with the familiar brake feel, engineers have developed a special simulator which is linked to the tandem master cylinder and which moves the pedal using spring force and hydraulics. In other words, during braking, the actuation unit is completely disconnected from the rest of the system and serves the sole purpose of recording any given brake command. Only in the event of a major fault or power failure does SBC automatically use the services of the tandem master cylinder and instantly establishes a direct hydraulic link between the brake pedal and the front wheel brakes in order to decelerate the car safely.
WORKING PRINCIPLE
Working principle Driver presses the brake pedal when braking is required Electric impulses are used to pass the driver’s braking commands Optimum pressure is calculated for each wheel Motor pumps the required pressure of the oil The result is reported to the microcomputer
It is not just in emergency braking that Sensotronic Brake Control proves its worth, but also in other critical situations - for example, when there is a risk of swerving.
Under such conditions, the system interacts with the Electronic Stability Program (ESP) which keeps the vehicle safely on course through precise braking impulses at all wheels and/or by reducing engine speed. SBC once again offers the benefits of greater dynamics and precision: thanks to the even faster and more accurate braking impulses from the SBC high-pressure reservoir, ESP is able to stabilize early and comfortably a vehicle which is about to break away.
EMERGENCY BRAKING
SBC recognizes the driver’s rapid movement from the accelerator onto the brake pedal as a clue to an imminent emergency stop and responds automatically with the aid of the high-pressure reservoir, the system increases the pressure inside the brake lines and instantly presses the pads onto the brake discs so that they can get a tight grip the moment the driver steps onto the brake pedal
COMFORTABLE BRAKING
Both the separation of the SBC pedal from the rest of the brake system and the proportional pressure control using Mechatronics serve to increase brake comfort – particularly during sharp deceleration or when the anti-lock braking system is operational. The usual vibration of the brake pedal when ABS sets in does not occur, which, is not only a comfort feature of the new system but also offers measurable safety benefits. Their research in DaimlerChrysler’s Berlin driving simulator has revealed that almost two thirds of all drivers are startled when ABS pulsation sets in: they do not increase the brake force further and are even prone to taking their foot off the brake pedal for a short while, thereby lengthening the stopping distance of their vehicle by an average of 2.10 meters during ABS braking from 60 km/h on a snow-covered road surface.
SOFT-STOP FUNCTION
Sensotronic Brake Control offers additional advantages in everyday driving situations - when slowing down ahead of traffic lights, in the wet, in traffic jams or hill starts:
The so-called Soft-Stop function of the SBC software ensures particularly gentle and smooth stopping which provides significant comfort benefits particularly around town when you need to slow down frequently for traffic lights. On a wet road surface the system metes out short brake impulses at regular intervals to ensure that the water film on the brake discs dries off and that SBC can always operate with optimum effectiveness.
This automatic dry-braking function is activated at regular intervals when the car's windscreen wipers are running. The driver does not even notice these ultra-precise brake impulses.
The Sensotronic Brake Control also incorporates a so-called Traffic Jam Assist function, which is activated using the cruise control stalk while the car is stationary. The benefit is that during stop-and-go traffic drivers only need to use the accelerator pedal; once they take their foot off the accelerator, SBC slows down the car to standstill at a steady rate of deceleration. The Traffic Jam Assist facility can remain operational up to 60 km/h and switches off automatically at higher speeds.
CONCLUSION
Sensotronic Brake Control is the brake of the future. The interdisciplinary interaction of mechanics and electronics provides its greatest benefits – the microcomputer, software, sensors, valves and electric pump work together and allow totally novel, highly dynamic brake management. The push onto the brake pedal feels like it always did. But starting from the master cylinder it doesn't continue hydraulically, but electronically. Sensors obtain the pressure and the speed, with which it builds up. This information is passed electrically to the controller, which then calculates the brake force - as described above. If the electricity fails and SBC stops working, the good old hydraulic will be used instead, and the car decelerated via the front wheels.