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About this book

Braking systems have been continuously developed and improved throughout the last years. Major milestones were the introduction of antilock braking system (ABS) and electronic stability program. This reference book provides a detailed description of braking components and how they interact in electronic braking systems.

Table of Contents


Motor-vehicle safety

In addition to the components of the drivetrain (engine, transmission), which provide the vehicle with its means of forward motion, the vehicle systems that limit movement and retard the vehicle also have an important role to play. Without them, safe use of the vehicle in road traffic would not be possible. Furthermore, systems that protect vehicle occupants in the event of an accident are also becoming increasingly important.
Wulf Post

Basic principles of vehicle dynamics

A body can only be made to move or change course by the action of forces. Many forces act upon a vehicle when it is being driven. An important role is played by the tires as any change of speed or direction involves forces acting on the tires.
Friedrich Kost

Car braking systems

Braking systems are indispensable for the roadworthiness and safe operation of a motor vehicle in road traffic conditions. They are therefore subject to strict legal requirements. The increasing effectiveness and sophistication demanded of braking systems over the course of time has meant that the mechanical systems have been continually improved. With the advent of microelectronics, the braking system has become a complex electronic system.
Wulf Post

Car braking-system components

Along with steering and changing gear, braking is one of the most frequently performed operations when driving a car. The components of the braking system must take account of that fact by making optimum use of the force applied to the pedal by the driver and by ensuring that the force required remains as constant as possible for the desired braking effect.
Wulf Post

Wheel brakes

There are two types of brake used on cars – disk brakes and drum brakes. New cars are now fitted exclusively with disk brakes at the front, and there is an increasing trend towards disk brakes for the rearwheels aswell. Both types are friction brakes in which the braking energy transmitted by the braking system acts by pressing the brake pads or shoes against the brake disks/drums.
Wulf Post

Antilock braking system (ABS)

In hazardous driving conditions, it is possible for the wheels of a vehicle to lock up under braking. The possible causes include wet or slippery road surfaces, and abrupt reaction on the part of the driver (unexpected hazard). The vehicle can become uncontrollable as a result, and may go into a slip and/or leave the road. The antilock braking system (ABS) detects if one or more wheels are about to lock up under braking and if so makes sure that the brake pressure remains constant or is reduced. By so doing, it prevents the wheels from locking up and the vehicle remains steerable. As a consequence the vehicle can be braked or stopped quickly and safely.
Heinz-Jürgen Koch-Dücker, Ulrich Papert

Traction control system (TCS)

Critical driving situations can occur not only while braking, but also whenever strong longitudinal forces should be transferred at the contact area between the tire and the ground. This is because the transferable lateral forces are reduced by this process. Critical situations can also occur when starting off and accelerating, particularly on a slippery road surface, on hills, and when cornering. These kinds of situations can overtax the driver not only causing him/her to react incorrectly but also causing the vehicle to become unstable. The traction control system (TCS) solves these problems, providing the vehicle remains within the physical limits.
Frank Niewels, Jürgen Schuh

Electronic stability program (ESP)

Human error is the cause for a large portion of road accidents. Due to external circumstances, such as an obstacle suddenly appearing on the road or driving at inappropriately high speeds, the vehicle can reach its critical limits and it becomes uncontrollable. The lateral acceleration forces acting on the vehicle reach values that overtax the driver. Electronic systems can make a major contribution towards increasing driving safety.
Thomas Ehret

Automatic brake functions

The possibilities of today’s electronic brake systems go far beyond the tasks for which they were originally designed. Originally the antilock braking system (ABS) was only used to prevent the wheels of a vehicle from locking up and therefore to ensure the steerability of the vehicle even during emergency braking. Today, the brake system also controls the distribution of the braking-force. The electronic stability program (ESP), with its ability to build up brake pressure independently of the position of the brake pedal, offers a whole series of possibilities for active brake intervention. The ESP is intended to assist the driver by applying the brakes automatically and to therefore provide the driver with a higher level of comfort and convenience. Some functions, however, enhance the vehicle safety since automatic brake application during an emergency results in shorter braking distances.
Jochen Wagner

Hydraulic modulator

The hydraulic modulator forms the hydraulic connection between the master cylinder and the wheel-brake cylinders and is therefore the central component of electronic brake systems. It converts the control commands of the electronic control unit and uses solenoid valves to control the pressures in the wheel brakes.
Frank Heinen, Peter Eberspächer

Sensors for Brake Control

Sensors register operating states (e. g. engine speed) and setpoint/desired values (e. g. accelerator- pedal position). They convert physical quantities (e. g. pressure) or chemical quantities (e. g. exhaust-gas concentration) into electric signals.
Erich Zabler

Sensotronic brake control (SBC)

Sensotronic brake control (SBC) is an electrohydraulic brake system that combines the functions of a brake servo unit and the ABS (antilock braking system) equipment, including ESP (electronic stability program). The mechanical operation of the brake pedal is redundantly measured by the actuator unit and transmitted to the control unit. There, control commands are calculated according to specific algorithms and passed to the hydraulic modulator where they are converted into pressure modulating operations for the brakes. If the electronics fail, a hydraulic fallback system is automatically available.
Bernhard Kant

Active steering

The development of vehicle steering systems is characterized by the consistent introduction of hydraulic servo assist and the replacement of ball-and-nut-type steering in the car by the easier and more inexpensive rack-and-pinion steering. Recently, electromechanical power steering has been displacing hydraulic power steering in small and lightweight cars. By law, however, pure “steer-by-wire” technology is not yet permitted in motor vehicles. European Union safety regulations still require a mechanical connection between the steering wheel and the wheels of the vehicle.
Wolfgang Rieger

Occupant protection systems

In the event of an accident, occupant protection systems are intended to keep the accelerations and forces that act on the passengers low and lessen the consequences of the accident.
Bernhard Mattes

Driving assistance systems

On average, someone dies every minute somewhere in the world as a result of a traffic accident. Bosch pursues the aim of reducing the frequency and the severity of accidents by developing active and passive driving assistance systems.
Peter Knoll

Adaptive cruise control (ACC)

ACC (Adaptive cruise control) simplifies the task of driving a car because it relieves the driver of the mentally demanding task of keeping a check on the car’s speed, thus allowing driving behind slower vehicles to be relaxed and safe.
Hermann Winner, Klaus Winter, Bernhard Lucas, Hermann Mayer, Albrecht Irion, Jens Lüder, Hans-Peter Schneider

Parking systems

On virtually all motor vehicles, the bodies have been designed and developed in such a way as to achieve the lowest possible drag coefficient values in order to reduce fuel consumption. Generally speaking, this trend has resulted in a gentle wedge shape which greatly restricts the driver’s view when maneuvering. Obstacles can only be poorly discerned – if at all.
Peter Knoll


Drivers have to process a constantly increasing stream of information originating from their own and other vehicles, from the road, and from telecommunications equipment. All this information must be conveyed to drivers in the information and communications areas of the vehicle on suitable display and indicating equipment that comply with ergonomic requirements. In the future, in-car cellular phones, navigation systems, and distance control systems will join automotive sound systems and vehicle monitoring systems as standard equipment in motor vehicles.
Bernhard Herzog

Orientation methods

In order to be able to understand various terms applied in road traffic, such as position- finding by means of satellite, and vehicle navigation, a number of the important basic terms associated with orientation and navigation methods are dealt with below.
S. Rehlich, M. Neumann, Marcus Risse, Wolfgang Baierl, Gerald Spreitz

Navigation systems

Navigation in the vehicle is defined as the process of directing the driver to his/her intended destination by means of direction arrows and voice-output instructions. Guidance along the route uses a digital road map and navigation satellites. Dynamic navigation also makes use of digitally coded traffic reports.
Ernst-Peter Neukirchner, Ralf Kriesinger, Jürgen Wazeck

Workshop technology

More than 30,000 garages/workshops around the world are equipped with workshop technology, i.e. test technology and workshop software from Bosch. Workshop technology is becoming increasingly important as it provides guidance and assistance in all matters relating to diagnosis and troubleshooting.
Stephan Sohnle, Rainer Rehage, Rainer Heinzmann


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