For the Emergency Steer Assist to work, it is essential that the vehicle is fitted with sensors for monitoring the road as far ahead as possible.
“The more reliable and detailed a picture of other road users and of the road itself can be gained, the more effectively Emergency Steer Assist can assist the driver to decide, for example, whether to take evasive action by steering to the left or the right when suddenly coming up against the tail of a motorway traffic jam”, said Bernd Hartmann, Chassis Systems Advanced Engineering manager in the Chassis & Safety Division.
The first stage will employ radar sensors similar to those currently in production for Adaptive Cruise Control (ACC). The advanced engineering department is also working on combining the video images from camera systems, like those already in series production for Intelligent Headlamp Control, with the radar signals. In this way, the chassis will learn to ‘see’ so that the vehicle’s safety systems are given early warning of an imminent hazard situation.
This will place the vehicle in a ‘safety mode’. “From this instant, the objective is to avoid an accident; comfort considerations are of secondary importance”, said Hartmann. In preparation for the obstacle-avoidance maneuver, the aim is to maximize the vehicle’s road-holding ability.
In those decisive seconds, the ESC is prepared to keep the vehicle on the road during the rapid avoidance maneuver and to stabilize it by the selective and early application of initial braking pressure to individual wheels. A further conceivable option for the future for vehicles equipped with active roll stabilization or adaptive chassis systems is to adjust the suspension and damper characteristics to the ‘hard’ mode.
The decision as to whether to brake before reaching the obstacle or to steer past it will always remain one for the driver to take. The assistance system will warn the driver that he is about to come across a dangerous situation.
The warning could be issued as an acoustical or it could even take the form of a haptical warning signal, the perceptible application of initial braking pressure, for example, or counterforce exerted by Continental’s active Accelerator Force Feedback Pedal. If the driver decides to take evasive action, the system calculates in milliseconds what line the optimum evasive maneuver, the so-called vehicle movement trajectory, could follow.
Any turn to avoid an obstacle should be carried out with a smooth steering movement so that the vehicle remains stable. By comparing the intended steering angle with the one actually chosen, Emergency Steer Assist determines whether the driver has steered sharply enough or possibly too sharply and can assist him by applying a light force in the steering wheel. “However, in this situation too, the ultimate decision always lies with the driver; if the situation demands it, he can disregard Emergency Steer Assist’s offer of help”, said Dr. Laier, Vice President of the Chassis Components business.