Sensotronic Braking System - Online Article

The most vital component in the runningand control of the modern vehicles is the braking system. In order to bring themoving motor vehicle to rest or slow down in a shortest possible time, theenergy of the motion possessed by the vehicle must be converted into some otherform of energy. The rate of slowing down or retardation is governed by thespeed of the conversion of energy. Kinetic energy is the energy of motion,which is converted into heat given up to the air flowing over the braking system.For realizing the full potentialities of engine and road holding safety, it isnecessary to bring the vehicle rapidly to rest from any speed by some means.This necessitates a lot of research on recent trends in braking systems. Thispaper aims at presenting the implementation of sensors in braking systems, andalso discusses the development of sensotronic braking systems.

Sensotronic Brake Control is the namegiven to an innovative electronically controlled brake system.It is an electro hydraulic brakingsystem in which there is no conventional direct mechanical-hydraulic linkbetween the brake pedal and the wheel brake under normal operating conditions

Itmarks an important milestone in the development of braking technology andpushes open the door to the futuristic world of "by-wire" systems.This technology communicates the driver's commands electronically via cable,rather than mechanically or hydraulically, as has traditionally been thecase.Sophisticated microelectronics take the place of many previouslymechanical components. And a powerful microcomputer, which is integrated intothe data network of the car and processes information from a series ofelectronic control units, oversees the operation of the system. The voluminousvacuum-powered brake booster is no longer required and the brake pedal and mainbrake cylinder merge into a single "activation unit". This unit ishydraulically decoupled from the remaining parts of the system by valves andserves merely to record the braking command. Sensors recognise the pressure inthe main brake cylinder and the speed at which the brake pedal is pressed, andpass this data on to the SBC computer in the form of electrical impulses.Whatmakes the system even more sophisticated is the fact that SBC calculates thebrake force separately for each wheel.

Introduction

It goes without sayingthat the brakes are the essential components of an automobile. They play amajor role not only in stopping the vehicle at shortest possible time but alsomaintain the stability of the vehicle. The brakes fitted to the vehicle shouldbe effective, safe in operation, progressive and consistent in response topedal as well as reasonably easy to adjust. Because of the importance of thebraking systems to an automobile, it is therefore not a surprise that many technologicalchanges have been taking place in the braking system technology. Theadvancement made in the field of braking technology not only ensured effectivebraking and vehicle stability but also eliminates the stress to the driver.

Sensortronic Breaking Systems

The Hi-techBrake of the Future

SensotronicBrake Control is the name given to an innovative electronically controlledbrake system which will fit to future vehicles. This system is regarded as yetanother important milestone to enhance driving safety. With Sensotronic BrakeControl electric impulses are used to pass the driver’s braking commands onto amicrocomputer which processes various sensor signals simultaneously and,depending on the particular driving situation, calculates the optimum brakepressure for each wheel. As a result, this system offers even greater activesafety than conventional brake systems when braking in a corner or on aslippery surface.The driver's brake command istransmitted electronically to a powerful micro-computer, which simultaneouslyprocesses data on the current ride status from a variety of sensors and usesthis to calculate and meter the ideal brake pressure for each wheel.

Components of Sensortronic Breaking Systems

     
  • Microcomputer 
  • High Pressure Accumulator 
  • Hydraulic Unit

Microcomputer

The data on the operation of the brake pedal, sensorsignals relating to other electronic assistance systems are collected here:Automated Braking systems supplies information on the speed of the wheels,provides data from its steering angle, rotational speed and lateralacceleration sensors and the electronic management systems for the engine andtransmission transmit the relevant engine or engine braking effect and thecurrent driving stage through a high-speed data line.

These calculations result in high-speed brake commandswhich ensure the highest degree of deceleration and ride stability for eachparticular driving situation. This system calculates the braking force for eachwheel individually.

High Pressure Accumulator

The high-pressure accumulator contains the brake fluidwhich flows into the system at a pressure of 140 to 160 bars. The computer regulates this pressure and alsocontrols the electric

Pump connected to the accumulator. This ensures shortresponse times and a rapid build-up of pressure.

Hydraulic Unit

This component essentially consists of the four wheelpressure modulators. They meter the brake pressure according to requirementsand pass it to the brakes. The specifications of the microcomputer areimplemented in this manner and each wheel is individually broken in such a wayas to ensure ride stability and the greatest possible deceleration. Fourpressure sensors in the wheel pressure modulators and one pressure sensor eachfor the hydraulic accumulator and for the brake commands monitor the processes.

Operational Features of Sensotronic Brake Control

Thefirmer the push, the higher the pressure in thebrake lines, and the higher the force exerted by the brake padsonto the brake disc. As the driver's brake commands are processed by acomputer, which also continuously receives sensor signals from each individualwheel and the steering system. From these data the optimal brake pressure iscalculated for each wheel individually.

Is advantageous, when braking with full force,when braking in curves or on slippery surfaces. But starting from the mastercylinder it doesn't continue hydraulically, but electronically. Sensors obtainthe pressure and the speed, with which it builds up. This information is passedelectrically to the controller, which then calculates the brake force - asdescribed above. If the electricity fails and computer stops working, the oldhydraulics can be used instead, and the car decelerated via the front wheels.

Brake Pedal: Electronics instead of Vacuum

In theSensotronic Brake Control, by contrast, a large number of mechanical componentsare simply replaced by electronics. The brake booster will not be neededeither. Instead sensors gauge the pressure inside the master brake cylinder aswell as the speed with which the brake pedal is operated, and pass these datato the computer in the form of electric impulses. To provide the driver withthe familiar brake feel, a special simulator which is linked to the tandemmaster cylinder and which moves the pedal using spring force and hydraulics.Depending on the pedal force, the master brake cylinder builds up theappropriate amount of pressure in the brake lines which – in a tried and testedinteraction of mechanics and hydraulics - then presses the brake pads againstthe brake discs via the wheel cylinder.

Control Unit: Pressure modulators for each wheel

The central controlunit is the centerpiece of the electro hydraulic brake. This is where theinterdisciplinary interaction of mechanics and electronics provides itsgreatest benefits – the microcomputer, software, sensors, valves and electricpump work together and allow totally novel, highly dynamic brake management:The transmission control unit finally uses the data tocommunicate the current driving range. The result of these highly complexcalculations is rapid brake commands which ensure optimum deceleration anddriving stability as appropriate to the particular driving scenario. What makesthe system even more sophisticated is the fact that computer calculates thebrake force separately for each wheel.

Emergency Braking: Stopping distance reduced by up to three per cent

The main performancecharacteristics of Sensotronic Brake Control include the extremely highdynamics during pressure build-up and the exact monitoring of driver andvehicle behaviour using sophisticated sensors. Thus moving into new dimensionsof driving safety. Already recognizes the driver’s rapid movement from theaccelerator onto the brake pedal as a clue to an imminent emergency stop andresponds automatically.

With the aid of thehigh-pressure reservoir, the system increases the pressure inside the brakelines and instantly presses the pads onto the brake discs so that they can geta tight grip the moment the driver steps onto the brake pedal. The stoppingdistance of an sensotronic brake equipped vehicle is cut by around three percent compared to a vehicle featuring conventional braking technology. The quickpressure build-up and the automatic periling of the wheel brakes leads to ashorter braking distance.

Drivingstability: Precise braking impulses for perfect performance

It is not just in emergency braking that Sensotronic Brake Controlproves its worth, but also in other critical situations – for example, whenthere is a risk of swerving. Under such conditions, the system interacts withthe Electronics which keeps the vehicle safely on course through precisebraking impulses at all wheels and/or by reducing engine speed. This systemonce again offers the benefits of greater dynamics and precision.

Braking Incorners: Greater safety due to variable brake force distribution

Even when braking incorners, this braking system also offers more safety than a conventional brakesystem. While conventional brake systems always meter out the brake pressureequally to the inner and outer wheels, sensotronic braking system offers thepossibility of assigning brake forces in a way appropriate to the situation.Hence the system will automatically increase the brake pressure at the outerwheels because the higher vertical forces also allow them to transfer greaterbrake forces.

At the same time thebrake forces at the inner wheels are reduced to provide the higher corneringforces needed to stay on course. The result is a more stable braking behaviouralong with optimum deceleration values. The system is programmed in such a waythat, when slowing down from a high speed, the larger part of the brake forcecontinues to act on the front axle.

SBC Add-on Functions: Support systems to reduce driver strain

Soft stop

By causing a precisely meteredreduction of the brake boosting just before the vehicle comes to a stop,Softstop reduces the comfort-impairing jerk which is frequently felt whendrawing to a halt. The driver does not need to activate Softstop, and thefunction is automatically deactivated during hard or emergency braking.

Brake drying

Since SBC is capable of generating even very smallbrake pressures precisely, it is possible for it to remove the film of moisturewhich accumulates on the brake discs in wet conditions by briefly and lightlyapplying the brakes. This further reduces brake response and therefore brakingdistances

Traffic Jam Assist

The Sensotronic Brake Control also incorporates a so-called TrafficJam Assist function, which is activated using the cruise control stalkwhile the car is stationary. The benefit is that during stop-and-go trafficdrivers only need to use the accelerator pedal; once they take their foot offthe accelerator, SBC slows down the car to standstill at a steady rate ofdeceleration. The Traffic Jam Assist facility can remain operational up to 60km/h and switches off automatically at higher speeds.

SBC Hold

A "drive-away assistant" prevents the vehicle fromrolling backwards or forward when starting on a hill or steep incline. A firmpush onto the brake pedal, and the car remains stopped, even when taking thefoot off the brake pedal, until the driver accelerates and the vehicle beginsto roll. When set, the instrument cluster indicates “SBC HOLD”.

Advantages of SBC over Conventional braking systems

Where there is a risk of skidding

Sensotronicsystem collaborates with the sensors, which keeps the vehicle safely on trackusing specific brake impulses at individual wheels and/or by reducing theengine torque. Here too this system makes full use of the advantages of higherdynamism and precision: as a result of even more rapid and even more finelymetered brake impulses from the high-pressure accumulator, this system canstabilize a swerving vehicle early and, at the same time, comfortably.

Dry - Brake

The dry brake function always activatedwhen the windshield wipers run. The sensors then senses, that it rains and,with short brake pulses unnoticed by the driver, keeps the brake discs alwaysdry and fully functional by the driver. Rain poses another problem for braking.Water coats the surface of the brake rotors and acts as a low friction surfacebetween the brake pad and rotor. The Sensotronic system overcomes this byslightly applying the brake pads against the rotors for a short time every fewminutes so that the water film is squeezed off the brake rotor and the rotor isheated by the friction to keep it dry.

     
  1. The main advantage ofthe electro-hydraulic brake SBC is that it raises braking comfort. 
  2. It reduces the time for application of breaks.And reduces the breaking distance by 3%. 
  3. TheSoft-Stop-Function provides for a softand smooth stop during normal braking. 
  4. The Traffic JamAssistant brakes the vehicle withpre-defined deceleration when it senses that the vehicle is in traffic. 
  5. The Drive-AwayAssistant prevents the car rolling backward on a hill and simplifies thedrive-away process. 
  6. The Dry BrakeFunction, where on wet roads the SBC carries out regular short and weak brakeapplications to wipe the water film off the brake discs. 
  7. reduces the time forapplication of breaks 
  8. Reduced requirementfor Stability Control, because braking force can be varied laterally duringcornering.

Future Technologies of SBC Systems

Theadvent of electronics in brake technology opens up new and promisingopportunities to the disciplines of safety and comfort. When it comes timeto stop a vehicle, most drivers slowly press on the brake pedal. Even during anemergency situation, almost all drivers will press only partially on the brakepedal for the first few milliseconds and then the brake pedal is pressedfirmly. This slight delay in braking enables the vehicle to travel severalmeters further and can mean the difference between a controlled stop and anaccident.

Sensotronic Brake reduces oreliminate as much as possible these factors with their new brake systems.Actual brake application begins long before the driver pushes on the brake pedal.By monitoring the accelerator pedal position, the brake computer can measurethe rate at which a driver releases the pedal. If a driver is removing his footquickly, then it could be in response to an emergency situation. The brakecontroller reacts by applying slight hydraulic pressure to each brake caliperto move the brake pads toward the brake rotor, eliminating this delay inapplying braking force. The computer measures the rate of brake pedalapplication by the driver and if the response is rapid, the computer will applythe brakes fully, even before the driver realizes that maximum braking effortis required.

Conclusion

The conventionalbraking systems have the disadvantage of causing excessive fatigue to thedriver under extreme braking conditions. With the help of sensotronic brakingsystems the above disadvantage is being efficiently overcome with the help ofsensors.

The sensotronicbraking systems can be considered as the future brakes of all automobiles dueto its efficiency and reliability.

This braking systemeliminates the need of appropriate pressure for appropriate type of braking asthe sensors play an important role in sensing the pressure of the drivers brakepedal and employ the required amount of braking.

In this system thereis no risk of leakage of either oil or air from the cylinders as the entirecontrol is carried out by a central computer which coordinates the differentcomponents of the braking system.

The sensotronicbraking systems can be commonly called as the “intelligent braking systems”.

The most vital component in the runningand control of the modern vehicles is the braking system. In order to bring themoving motor vehicle to rest or slow down in a shortest possible time, theenergy of the motion possessed by the vehicle must be converted into some otherform of energy. The rate of slowing down or retardation is governed by thespeed of the conversion of energy. Kinetic energy is the energy of motion,which is converted into heat given up to the air flowing over the braking system.For realizing the full potentialities of engine and road holding safety, it isnecessary to bring the vehicle rapidly to rest from any speed by some means.This necessitates a lot of research on recent trends in braking systems. Thispaper aims at presenting the implementation of sensors in braking systems, andalso discusses the development of sensotronic braking systems.

Sensotronic Brake Control is the namegiven to an innovative electronically controlled brake system.It is an electro hydraulic brakingsystem in which there is no conventional direct mechanical-hydraulic linkbetween the brake pedal and the wheel brake under normal operating conditions

Itmarks an important milestone in the development of braking technology andpushes open the door to the futuristic world of "by-wire" systems.This technology communicates the driver's commands electronically via cable,rather than mechanically or hydraulically, as has traditionally been thecase.Sophisticated microelectronics take the place of many previouslymechanical components. And a powerful microcomputer, which is integrated intothe data network of the car and processes information from a series ofelectronic control units, oversees the operation of the system. The voluminousvacuum-powered brake booster is no longer required and the brake pedal and mainbrake cylinder merge into a single "activation unit". This unit ishydraulically decoupled from the remaining parts of the system by valves andserves merely to record the braking command. Sensors recognise the pressure inthe main brake cylinder and the speed at which the brake pedal is pressed, andpass this data on to the SBC computer in the form of electrical impulses.Whatmakes the system even more sophisticated is the fact that SBC calculates thebrake force separately for each wheel.

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Comments

Rajesh Kumar Gupta on 2009-02-17 23:40:04 wrote,

Nice writeup man, keep it up.

Vikash Jaiswal on 2009-02-18 14:33:28 wrote,

it increases my technical knowledge

Aditya Prabhakar on 2009-02-18 19:53:24 wrote,

Thank You :)

Mani Kantan on 2009-04-10 17:55:28 wrote,

nice info, can i get more info of in which vehicle it is being used now n future developements