New Technology in Driver Assistance

About one third of all car accidents are due to collisions with other vehicles or objects on the road. In almost 50 percent of such accidents, the driver doesn’t brake at all or, in another 20 percent, is much too hesitant.

Many of these crashes will in future be prevented by Predictive Safety Systems, electronic systems that actively attempt to prevent cars crashing. Robert Bosch GmbH, the world’s second largest supplier to the automotive industry, intends to combine Antilock Braking System (ABS), Electronic Stability Program (ESP) and Hydraulic Brake Assistant (HBA) with the radar sensor of Adaptive Cruise Control (ACC) and, in future, also video sensors.

"Based on the information received by the sensors on distance, relative speed and size of preceding vehicles, the systems are capable of activating the safety functions even before the imminent crash", says Dr. Bernd-Josef Schäfer, Vice President, Business Unit Driver Assistance Systems, Bosch Automotive Electronics Division.

“Vehicle developers can further improve the effectiveness of current active and passive safety systems if they include information about the vehicle's environment,” he says.

Bosch plans to develop the Predictive Safety Systems in three stages.

1. Stage 1 - the system prepares the brake system for a possible emergency braking

In situations where there is the threat of an accident, the Predictive Safety Systems prepares for it by building up brake pressure, brings the brake pads into very light contact with the brake discs and modifies the hydraulic brake assist.

The result is that the driver gains important fractions of a second until the full braking effect is achieved. If he then undertakes emergency braking, he gets the fastest possible braking action with the maximum deceleration and thus the shortest stopping distance. If he does not need to brake, these preparatory measures are withdrawn.

Even if there is an accident, the system can reduce the side-effects and save lives. A typical situation which can lead to an accident is when a much slower vehicle moves out into the lane in which you are driving on the motorway. If you are driving at 140 km/h and the vehicle in front moves into your lane 40 metres ahead of you travelling at only 80 km/h, the Predictive Safety System prepares for emergency braking in only a fifth of a second – before you have even noticed the slow-moving obstacle. In the event of emergency braking, the driver benefits from the more rapid operation of the braking system, enabling him to avoid an accident: without the Predictive Safety System there would have been a serious accident.

Bosch is planning the series introduction of the first generation of the Predictive Safety System for 2005.

2. Stage 2 - Warning where there is the danger of colliding with the vehicle in front

The second generation of the Predictive Safety System does not only prepare the braking system, it also gives a timely warning to the driver about dangerous traffic situations, helping in many cases to prevent accidents.

To do this it triggers a short, sharp operation of the brakes. Studies of drivers have shown that a sudden braking impulse is the best way of drawing the driver's attention to what is happening on the road; drivers react directly to the warning. The system can also warn the driver by means of visual or sound signals, or by a brief tightening of the normally loosely-fastened safety belt.

In the case outlined above where a vehicle moves into the lane in front of you, the extended Predictive Safety System prepares for emergency braking in only a fifth of a second. The difference from the first generation of the safety system is that the driver is also given a warning if he does not change course or brake within the next third of a second.

In this case, the driver can still avoid a crash by moving out of the lane. If he only brakes, he can at least considerably reduce the speed of his vehicle.

Series launch of the 2nd generation of the Predictive Safety System with the warning function is planned by Bosch for 2006.

3. Stage 3 - Emergency braking in unavoidable collisions

The third developmental stage of the Predictive Safety System will not only recognize an unavoidable collision with a vehicle in front, but the system will in this instance also trigger automatic emergency braking with maximum vehicle deceleration.

This will reduce the severity of an accident when the driver has failed to react at all to the previous warnings, or has reacted inadequately.

Automatic control of vehicle function demands a very high level of certainty in the recognition of objects and the assessment of accident risk. In order to be able to reliably recognize that a collision is inevitable, further systems – such as video sensors – will have to support radar sensors. It will also be necessary to create the legal basis for the use of such systems for traffic on public roads.

Video Cameras and Lane Holding

The video camera developed by Bosch is fitted behind the windscreen, situated within the area of the screen swept by the wiper blades so that its field of vision is kept free of dirt and water drops.

Bosch uses CMOS (Complementary Metal Oxide Semiconductor) semiconductor technology for the image sensor. The incident light is converted into electrical impulses by the sensor's image elements – the pixels. The impulses are then converted in the analogue-digital conversion into information on the level of brightness of each individual pixel. The CMOS sensor can clearly distinguish very bright sources of light from the background and present the overall image without over-exposure.

This means that the camera is ideally suited for use in vehicles.

It "sees" the area in front of the vehicle and when combined with a powerful computer and good-quality image processing, can support the driver in many different ways.

For lane recognition, for example, the video camera detects the course of the road or lane in front and the road or lane boundaries. A fast computer simultaneously processes the image signals captured by the camera. The computer uses special software developed by Bosch which makes use of data derived from computer modelling – for example, on typical courses of roads or the layout of intersections.

If the system detects that the vehicle is unintentionally drifting out of the lane or off the road, it sends a warning to the driver. Depending on the application, the warning may be given by sound or by vibrations sent to the driver's seat or the steering wheel.

A lane-holding assistance function is being developed for the next generation of the system. Precisely targeted steering impulses support the driver when the vehicle is in danger of unintentionally leaving the road. However, the driver can intervene, override the system support or even switch off the system completely.

In addition to lane recognition and lane-holding, Bosch's development engineers are assigning further assistance functions to the front-mounted video camera. For example, linking in the video system is seen as absolutely necessary for future extensions of the ACC system which currently uses a radar sensor.