Driver assistance systems: Intelligent co-pilots

Sep 12, 2005
  • DISTRONIC PLUS: proximity control at all speeds between zero and 200 km/h
  • Brake Assist PLUS: radar sensor for early detection of an accident risk
  • Park assist: radar-assisted parking and reversing
  • Night view assist: infrared headlamps for improved long-range visibility
In 1998 a long-held dream for many drivers was fulfilled in the S-Class with the DISTRONIC autonomous intelligent cruise control system: an electronic co-pilot which keeps the car at a set speed and at a set distance from the vehicle ahead – for more convenience and less stress. Mercedes-Benz was the world’s first auto-mobile manufacturer to offer its customers such a system.
Mercedes-Benz has developed this highly efficient assistance system even further for the new S-Class, hence the name DISTRONIC PLUS.
By combining the previous DISTRONIC radar (77 GHz) with a newly developed close-range radar (24 GHz), which is also used for Brake Assist PLUS, Mercedes engineers have been able to extend the working range of the proximity control system even further, so that it can now scan a distance of anything from 0.2 to 150 metres. While the 77-Gigahertz radar monitors the road ahead over a long distance, the signals from the 24-Gigahertz sensors have a range of around 30 metres and monitor the immediate vicinity of the vehicle. The electronic control unit analyses the information received from both radar systems and calculates the engine, automatic transmission and braking parameters required for proximity control.
In addition, the speed range for this control function has been increased from the previous 30 - 180 km/h to zero - 200 km/h. This means that when the traffic tails back, DISTRONIC PLUS automatically brakes the S-Class to a standstill and accelerates back to the set speed as soon as the traffic situation allows. To move off automatically, the driver only needs to operate the DISTRONIC stalk on the steering column or briefly depress the accelerator.
As before, the required interval can be set according to the traffic flow and density: using a control function on the DISTRONIC stalk, the driver is able to variably adjust the time lapse between one and two seconds if required by the traffic situation. The medium setting corresponds to a time lapse of 1.5 seconds, representing a gap of around 42 metres at a speed of 100 km/h. The target and actual distances between the S-Class and the vehicle ahead are shown in the central display of the instrument cluster.
Automatic braking to a standstill
As more dynamic proximity control intervention is often required at lower speeds, i.e. in stop-and-go traffic with frequent starting and braking, the acceleration and deceleration values of the system have been reconfigured. Depending on the speed, automatic deceleration of up to four m/s² (previously two m/s²) is now possible. If DISTRONIC PLUS detects that heavier braking is required, a warning light appears in the instrument cluster. This is accompanied by an audibile warning which tells the driver to watch the traffic situation and apply the brakes himself if necessary.
The electronic proximity control system can be activated independently of DISTRONIC PLUS. In this case too, the system continuously monitors the distance from the vehicles ahead and gives the driver an audibile warning if he is approaching another vehicle too rapidly at a speed of more than 30 km//h, and lights up a warning lamp if the gap is too small.
Brake Assist PLUS: two radar systems looking ahead
It was in 1992 that Mercedes engineers conducting tests in the driving simulator found that while the majority of male and female drivers operate the brake pedal rapidly in an emergency situation, they often do not do so with sufficient force. The braking performance is therefore not used to the full, and the braking distance is considerably increased. These findings led to the development of Brake Assist, which first entered series production in 1996 and has been standard equipment in all Mercedes cars since 1997.
The technology interprets a certain speed with which the brake pedal is depressed as an emergency braking situation, and builds up the maximum braking assistance within fractions of a second. This significantly shortens the vehicle’s braking distance – by up to 45 percent at 100 km/h on a dry road surface, for example.
Mercedes-Benz has expanded Brake Assist into an anticipatory system which assists the driver even more effectively than before in critical situations. The system is based on radar technology: it registers the distance from vehicles ahead, warns the driver if the gap is too small and calculates the necessary brake force assistance if a rear-end collision threatens. If traffic tails back and the driver is obliged to operate the brake pedal, the new Brake Assist PLUS instantly builds up the braking pressure required to manage the situation.
While a conventional Brake Assist system requires reflex braking, the new system already detects the driver’s braking intention as soon as the pedal is depressed and automatically optimises the brake pressure. This meets one of the major conditions for preventing rear-end collisions, namely the best possible deceleration for the situation in hand.
In addition to the 77-Gigahertz long-range proximity control radar, the anticipatory system Brake Assist PLUS, part of the DISTRONIC PLUS package, also uses a newly developed 24-Gigahertz short-range radar system. These systems complement each other: while the long-range DISTRONIC radar is configured to monitor three lanes of a motorway up to a maximum distance of 150 metres with an opening angle of nine degrees, the new 24-Gigahertz radar registers the situation immediately ahead of the vehicle with an angle of 80 degrees and a range of 30 metres.
Accident rate reduced by three quarters
Mercedes-Benz has intensively tested the effectiveness of this innovative technology in the driving simulator and in practical trials:
  • 100 male and female drivers took part in a series of tests in the driving simulator. They each completed a 40-minute journey with several critical situations on motorways and extra-urban roads in which it was only possible to avoid accidents by hard braking. The average accident rate, 44 percent in tests with conventional brake technology, was reduced by three quarters with Brake Assist Plus, to 11 percent.
  • More than 200 male and female drivers took part in practical trials in Europe and the USA, covering a total of more than 450,000 kilometres in 24 test cars. These journeys were recorded with the help of the latest measuring and video technology. Evaluation of the data and video sequences showed that Brake Assist PLUS also makes a major contribution to safety under real conditions.
Park assist: collision warning when reversing
Mercedes-Benz also uses the latest radar technology for the new park assist in the S-Class, which is available in conjunction with DISTRONIC PLUS and Brake Assist PLUS. This system uses the four close-range sensors at the front and two radar sensors in the rear bumper to assist the driver when parking or warn him of obstacles when reversing.
The newly developed system operates with a much greater range and coverage than PARKTRONIC, which is based on ultrasound technology. The radar sensors of park assist operate up to a distance of eleven metres and have an opening angle of 40 degrees, which means that the driver is warned of an impending collision much sooner. This is an advantage which becomes particularly obvious when reversing over a longer distance. In this case the system is active from a speed of seven km/h, and warns the driver with an audibile signal if a collision threatens. This allows enough time to prevent the collision with firm operation of the brake pedal.
When parking the vehicle, the system assists the driver within a speed range from zero to 16 km/h. When moving forward, the colour display in the instrument cluster shows two segments which indicate the distance from an obstacle within the range of the radar sensors on the left and right sides, thereby allowing the vehicle to be parked with absolute precision. When the first red segment lights up an intermittent warning is also sounded. A constant warning note is sounded when the second red segment is reached, informing the driver that the minimum distance has been reached. When reversing, a display in the rear roof lining is switched on and indicates the distance from any obstacles – once again for each side of the vehicle and with an acoustic warning over the last few centimetres.
Reversing camera provides precise guidance into parking slots
Optionally, the new S-Class can be supplied with the proven PARKTRONIC ultra-sound-based parking system. A special reversing camera provides further assistance. The reversing camera, mounted in the boot lid above the licence plate, is activated automatically when the driver engages selector position "R". It projects an image of the area behind the vehicle onto the COMAND display. Based on the vehicle dimensions, speed and steering angle, a control unit calculates the optimal path the vehicle should take into the parking slot. Coloured lines are super-imposed on the camera image to guide the driver.
Night view assist: significantly increased range of vision in the dark
The risk of serious injury in road traffic is much greater in twilight and in the dark than during daylight hours. Although average traffic density is reduced to only around 15 percent at night, more than one in three fatal traffic accidents occur at this time.
Mercedes-Benz has therefore been working for many years to improve nighttime driving safety. New developments like the xenon low-beam light (1995), bi-xenon headlamps (1999), the Active Light System (2003) and the cornering light (2004) have all made important contributions. Night view assist, which will make its European debut in the new S-Class and will be available as an option in conjunction with bi-xenon headlamps and Active Light System, is a further milestone in this field of automotive technology. Thus the package of lighting systems available for the new top-of-the-line Mercedes model is currently unrivalled in terms of lighting power and performance.
In the dark, the newly developed night view assist system provides the driver with a much greater range of vision than conventional low-beam headlamps, enabling the course of the road, pedestrians, cyclists and obstacles to be recognised much sooner. At the same time the system relieves driver stress during tiring journeys at night, keeping the driver fit enough to respond rapidly and appropriately in critical situations.
Infrared beams in the headlamps, camera on the windscreen
The innovative system has six main components:
  • The driver activates the system by means of a switch to the left of the rotary light switch. It must be dark outside and the low-beam headlamps must be switched on.
  • Two special searchlights in the headlamp housings illuminate the road ahead with invisible infrared light. When night view assist is active, these are automatically switched on when a speed of 15 km/h is reached, and remain on when braking down to about 10 km/h. Night view assist is not operational when reversing.
  • An infrared-sensitive camera on the inside of the windscreen records the scene ahead of the vehicle. A lens shade protects the camera against extraneous light reflections.
  • An electronic control unit processes the image from the infrared camera and transfers it to the display in the instrument cluster as a clear greyscale image.
As soon as night view assist is activated, the display in the centre of the instru-ment cluster switches over to show the camera image. The large eight-inch display is directly in the driver’s field of vision, and he can use it like the speedometer and cockpit instruments to glance down regularly, monitor the situation ahead of the S-Class as shown by the infrared image and adjust his driving accordingly. When the system is switched on, the speed indication changes from a dial instrument to a horizontal, bar-type display at the lower edge of the camera image.
Significantly increased safety in critical situations
Mercedes engineers examined the capabilities of this technology in a series of trials. During comparative test drives with low-beam bi-xenon headlamps and the new night view assist system, the male and female test drivers recognised obsta-cles in the road much sooner when assisted by the infrared light system. During tests, drivers were already able to discern test dummies at the roadside dressed in light-coloured clothing at a range of around 210 metres, which is about 41 metres sooner than with low-beam bi-xenon headlamps. The system proves even more effective in the case of pedestrians in dark clothing. In these situations the night view assist system already enabled the drivers to identify the test dummies at a range of around 164 metres, compared with only at about 72 metres when driving with low-beam bi-xenon headlamps alone. This represents a safety improvement of no less than 125 percent.
Even when the headlamps of oncoming vehicles dazzle the driver and severely obscure the view, visibility is much better with this assistance system: a test dummy in light-coloured clothing standing at the road edge 50 metres behind an oncoming vehicle was detected from an average distance of 140 metres with the help of night view assist – around 53 metres sooner than with low-beam bi-xenon headlamps.
LINGUATRONIC: voice control for radio, audio and navigation systems
For a number of years now, this Mercedes-Benz-developed voice control system has been establishing itself as an important assistance system which enhances both safety and convenience. In the new S-Class, the driver can use LINGUATRONIC (optional) to control the telephone, audio system and navigation system. After activating LINGUATRONIC using a button on the steering wheel, all the driver has to do is say the word - or words - and the radio will search for or store another station, switch to the next track on a CD or enter the desired destination in the navigation system. In this way LINGUATRONIC reduces driver stress, allowing him to devote more attention to the road and traffic conditions.