Driver assistance systems

The new A8 also demonstrates the innovative power of Audi in its assistance systems, offering a wide, newly echeloned range of high-tech systems. These systems regulate the distance to the car ahead, help the driver to change lanes and stay in the lane, and assist with parking. They recognize speed limit signs and see far ahead into the night. Compared with the competition, the systems in the new A8 are considerably more powerful and intelligent, thanks to their pioneering new networking.

The radar-aided automatic proximity control system, adaptive cruise control with stop & go, is a major advancement over its predecessor. It regulates the speed and the distance to the vehicle ahead by accelerating and braking in a speed range from 0 to 250 km/h (155.34 mph), and brakes automatically within certain limits. Because the ACC stop & go function works together with the navigation system, it knows the course of the route in advance.

The system, which Audi has subjected to more than 600,000 kilometers (372,000 miles) of field testing, is particularly convenient in stop & go traffic. It brings the new A8 to a stop roughly four meters behind the vehicle ahead with no intervention on the part of the driver. If the stop is brief, the sedan automatically resumes moving again; after a longer stop the driver must tap the accelerator or the cruise control lever. The driver can also anticipate and do this while the A8 is still stopped. The car is then ready to depart for the next 15 seconds and follows the vehicle ahead as soon as it begins rolling.

The two radar sensors play a major role in the performance of the system. They are installed in the air inlets at the front of the car and are automatically heated when it is cold. They transmit radar waves at a frequency of 76.5 gigahertz covering a 40 degree wedge-shaped field measuring 250 meters (820 ft) in length. A computer uses this to analyze the traffic situation in front of the vehicle and detect the preceding vehicles.

The driver can influence the function of the ACC stop & go; the interval to the vehicle ahead is adjustable in four steps and the three levels of control system dynamics have been defined. Acceleration and braking is comfortable. Deceleration is limited to 4 m/s2 – a good third of the maximum and subjectively equivalent to stepping on the brake pedal with medium force. The six-piston pump at the heart of the brake system generates the pressure very smoothly and harmoniously.

A broad network: more information
The adaptive cruise control with stop & go function is a highly intelligent system – thanks to its broad networking. It works closely together with other driver information systems, and each of then contributes its own specific strengths. All told, it takes data from 27 control units, with which it works to continuously analyze the complete area around the vehicle and compares the results extremely quickly. This high level of information enables the system to recognize complex scenarios and predictively support the driver.

For instance, if the vehicle driving ahead on a country road signals right and brakes because it wants to turn off, a conventional system only knows one way to react: it brakes analogously to the vehicle ahead and will even come to a stop in certain circumstances. The adaptive cruise control with stop & go in the A8 assesses the situation using all of its networked intelligence. It is aware of the intersection from the navigation system’s route data and uses the video images and the long-range radar to analyze the situation as it arises.

The system behaves just like the driver would: it brakes gently and lets the A8 approach closer to the turning vehicle. Once the driver decides to pass and signals to the left or turns the wheel, the ACC stop & go shifts its measuring area to the left and reapplies the gas – and the A8 quickly passes the other car.

The ACC stop & go also uses its networked knowledge in many situations on the highway in order to react intelligently and precisely. Whether another vehicle pull into the A8’s lane or the A8 is closing on a slow-moving vehicle in front of it, the system handles the situation calmly and coolly, making driving more fluid and harmonious. If the driver wants to pass, a second optional assistance system comes into play: Audi side assist.

Rearward-looking radar: Audi side assist
Audi side assist activates at speeds above 30 km/h (18.64 mph). Two 24-gigahertz radar systems in the rear observe what is happening behind the A8 to a distance of 70 meters. Their data are analyzed by a computer. If another vehicle moves into the critical zone – if it is riding in the blind spot or approaching rapidly from the rear – the so-called information stage is activated. A yellow LED indicator illuminates in the casing of the driver’s side mirror; the driver sees it only when looking directly into the mirror.

If drivers activate their turn signal to change lanes in spite of the warning, the indicator become brighter and flashes at a high frequency. This signal – the warning stage – can hardly be overlooked. The display is such that in practice it is only visible to the driver. Its brightness adapts to ambient light conditions and can also be adjusted via the MMI control terminal.

Keeps you in your lane better: Audi lane assist
Audi lane assist is another assistance system. At speeds above roughly 65 km/h (40.39 mph), Audi lane assist warns the driver when he or she is about to leave the lane inadvertently. A camera mounted in front of the rear-view mirror observes the road to a distance of 60 meters (197 ft) and a coverage angle of 40 degrees. It delivers 25 high-definition images per second. Sophisticated software processes the images, identifies the lane markings and the course the A8 is following between them.

If the driver allows the car to wander in the direction of a lane marking but has not indicated that he or she intends to make a turn, Audi lane assist warns the driver by vibrating the steering wheel. The vibration is generated by a vibration motor in one of the spokes; its intensity can be adjusted in three stages using the MMI. When this warning is given is also selectable – before the wheel touches the line, when crossing the line or at the discretion of the system.

Compared to the previous version, Audi lane assist has become much more powerful. For instance, the color camera can differentiate between the yellow line in construction zones and the white ones. It meets its limits under particularly unfavorable conditions, such as in the snow or if the road surface is very dirty. It informs the driver when this is the case.

The camera of Audi lane assist serves a number of important functions in addition to this primary function. It provides important imagery for the ACC stop & go – it can detect vehicles on the road ahead and recognize when they signal. Its data also go into the startup function in stop & go traffic. The camera’s images also play an important role in emergency braking initiated by Audi pre sense front and for the continuous headlight range control.

Speed assistant: the speed limit display
The camera in the base of the mirror is also used by an entirely new assistance system – the speed limit display that will be available from mid-2010. It detects the signs on the side of the road and their supplemental panels referring to wet conditions or times of day, for example. It shows the signs with the supplemental panels as graphics on the instrument cluster display, so that the driver can see the current speed limit at a glance.

The third eye: the night vision assistant
Also debuting in the new Audi A8 is the night vision assistant, which is activated via a button at the light switch. The heart of this system is a thermal imaging camera mounted behind the outer left of the four rings at the front of the car. It has a wide, 24-degree angle of view, and its protective window is cleaned when dirty and heated when cold.

As a far infrared system (FIR), the camera reacts to the heat radiated by objects. A computer transforms the information from the camera into black-and-white images and displays them on the central display located between the instruments. The view continuously tracks the road and the course of the A8.

The far infrared technology has significant strengths, particularly when compared to the competing near infrared systems. Independent of driving speed, it can look as far as 300 meters (984 ft) ahead, far beyond the range of the high beams, and therefore is not blinded by headlights and similar light sources. Most importantly, it concentrates on the essentials: animals and people. Regardless of whether they appear bright or dark to the human eye, they are conspicuously bright in the image due the heat they give off, whereas the cooler road appears dark.

The image processing software can detect persons at a range of 100 meters (328 ft) for even greater safety. When analyzing the data, it specifically seeks out human contours and objects that are bright and round – their heads, in other words. Traffic lights, tail lights, and similar light sources are subtracted out. Detected persons are highlighted with yellow markings on the display. If the control unit assumes a hazard because a person is walking on the road close to the car, for example, the person is highlighted in red and a warning gong sounds.

Audi made a conscious decision to not use the first-generation night vision devices, which did not have this highlighting function. Studies have shown that they tend to increase the burden on the driver in critical situations. The system in the new A8, however, relieves the burden on the driver by adjusting its range and warning thresholds to the speed driven, eliminating unnecessary irritations in many situations.

The marking, the gong, and image contrast can be configured via the MMI. Like every assistance system, the night vision assistant also works within certain, very liberal system limitations. Pedestrian highlighting is switched off at temperatures above 28 degrees Celsius, for example.

Help when maneuvering: the parking assist systems
Two optional parking assist systems in the new A8 make maneuvering more comfortable and safe. The parking system plus uses four ultrasonic sensors up front and in the rear to indicate the distance acoustically and graphically on the MMI display. The front sensors also monitor the starting zone immediately in front of the car for the ACC stop & go when the A8 is creeping along in traffic.

The parking system plus with reversing camera also uses an extremely light-sensitive external camera. Mounted in the trunk lid, its fish-eye lens covers a broad 130 degree field of view. The images generated by this camera are processed to remove distortion and displayed on the MMI operating system monitor. Guidelines and fields show the car’s projected path.

All driver assistance systems in the new A8 serve a common objective with their intelligent sensors, lightning-fast calculations, and high degree of integration: to support the driver in his or her work behind the wheel. They never force themselves on the driver, never make decisions for the driver, and never restrict the driver. Instead they make driving easier, more relaxed and smoother. That is because all Audi technology is focused on the person.

The equipment, data and prices specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.