Press Release
Brake Assist PLUS in test operations: Over 400,000 kilometres on the road, and 14 months on test rigs and in a driving simulator
- Practical tests with drivers in Europe and the U.S.
- Non-stop testing in taxis in Stuttgart, Germany
- Sustained testing under near-real conditions on the “hardware in the loop� test rig
- Successful testing with 100 test subjects in a driving simulator
There’s no substitute for reality � and recognition of this fact played a key role in the test operations conducted for the new Brake Assist (BAS) PLUS system. In order to test the radar-based system under tough everyday conditions, Mercedes engineers installed sensors in two dozen test vehicles that were driven more than 380,000 kilometres in Europe and the U.S. The new radar technology also underwent an additional series of tests for one year in a taxi in the German city of Stuttgart: The vehicle equipped with the system drove in congested urban traffic for a distance of approximately 40,000 kilometres, and a video camera in the S-Class saloon’s radiator grill recorded every kilometre travelled.
The tests focused on traffic situations in which the new radar technology had to differentiate between tight conditions (e.g. travelling through narrow streets with cars parked on the sides) and those situations actually more likely to lead to an accident.
The system’s measuring device and video camera recorded in parallel traffic data and images in each critical situation. Engineers used this information to directly compare the video images with the data recorded by the radar technology, thereby enabling them to make an objective assessment as to whether the close-proximity radar judged the traffic situation correctly, and actually sent the right control signals to the Brake Assist PLUS system.
The data collected under tough everyday conditions was also used to continually optimize the control unit’s software, and was incorporated into the computer simulation tests conducted in parallel as well.
Test rig: Combining the benefits of practical testing and simulation
“Hardware in the loop� is the name of a new procedure that combines the benefits of practical testing and computer simulation. In the case of Brake Assist PLUS, the procedure went beyond simply recreating critical driving situations on a computer; instead, it also incorporated the proposed BAS control unit into the testing process. Powerful computers fed the unit sensor data from simulated traffic situations and then monitored and recorded the control commands issued by the unit in response. The advantage of this procedure was that it enabled engineers to confront the Brake Assist PLUS control electronics with thousands of real traffic situations, which it had to react to correctly in an extremely short period of time.
Many of these testing runs involved an extensive catalogue of manoeuvres, including driving too close to the vehicle ahead or braking too late in heavy traffic. The radar technology in Brake Assist PLUS was forced to deal with moving and stationary obstacles and prepare for potential accidents � always with the goal of reliably recognizing objects in front of the vehicle and reacting to them appropriately. The test engineers also continually expanded the selection of critical traffic situations to include data gained from practical tests conducted in parallel with those undertaken with the test rig.
As was the case with the real-life tests, the simulations were marked by a certain “lack of clarity� so as to ensure that no one situation was completely like another. The engineers also supplied the unit with faulty data or data from false sources � i.e. "�electronic noise,� incorrect sensor data and simulated partial breakdowns of the system. All of these measures were designed to ensure that the system functions properly in all situations.
A network of computers operating in parallel spent well over a year recording the tests in real time. Weekends were particularly busy, as this was when the control unit was presented with approximately 1,400 critical situations that it had to reliably recognize, evaluate, and react to by issuing the correct commands to the PRE-SAFE® system in the virtual vehicle.
Driving simulator: Brake Assist PLUS significantly reduced accident rate
On its way to series production, the new Brake Assist PLUS system was also put through an unprecedented test program on the driving simulator operated by DaimlerChrysler Research in Berlin. In this series of tests, 100 men and women conducted 40-minute drives on virtual motorways and rural roads, during which time they had to deal with typical traffic situations in which accidents could be avoided only through emergency braking manoeuvres. The test subjects faced these situations both with and without Brake Assist PLUS in their virtual vehicles.
The new radar-sensor technology enabled the predictive system to recognize dangerous situations at an early stage and then support drivers with their braking manoeuvres. As such, the virtual vehicles with Brake Assist PLUS had considerably fewer accidents than those not equipped with the new system. The average accident rate fell from 44 to 11 per cent.
Moreover, the system helped mitigate the severity of the accidents that occurred in those cases where a collision could no longer be avoided because of the driver reacting too late. The braking-power support provided in line with the given situation also reduced impact speed by an average 21 km/h to 26 km/h.
