Assistance Systems From Audi

INGOLSTADT – November 3, 2008: A more relaxing ride, a safer journey: the innovative assistance systems offered by Audi on-board its range of models help to ensure stress-free driving. A driving force behind technical advances in this area as in others, Audi can, on request, equip its vehicles with high-tech systems deriving directly from the luxury class. These systems regulate the distance to the vehicle ahead, help the driver to change lanes and stay in lane, and assist with parking.

Over the past decades, passive and active safety systems have significantly reduced the number of accidents and lessened their effects. And Audi is taking this progress to new levels. The innovative assistance technologies can, like humans, monitor the areas around the car in order to make appropriate decisions and take the necessary actions. The Audi systems ensure relaxed, safe driving. They help the driver to maintain vigilance by reducing his workload but do not relieve him of responsibility.

From 30 to 200 km/h (19 to 124 mph): ACC maintains the distance
One system that aids the driver is radar-assisted automatic distance control. In the speed range from 30 to 200 km/h (19 to 124 mph), adaptive cruise control (ACC) maintains the preset speed, taking into account the distance to the vehicle in front. The system reacts to vehicles that are up to 180 meters (197 yards) away. The radar sensor detects whether and how the distance to the vehicle ahead is changing.

If the driver wishes to overtake at a higher speed, ACC can be overridden at any time by accelerating. The system remains active and subsequently continues to maintain the desired speed that has been selected or the preset distance. Pressing the brake pedal always switches off the system. It must then be restarted again at the control lever (resume). This reactivates the most recent setting.

The Doppler effect and signal duration: How ACC takes measurements
The radar sensor is located at the right, next to the single-frame grille, in an exposed housing with a plastic lens. The sensor’s scanning zone is ± 8°, and its range approximately 180 meters (197 yards). The radar sensor’s four transmitting/receiving units operate in the 76.5 GHz frequency range, which is licensed for radio signals, and the transmission frequency is modulated using a FMCW (frequency-modulated continuous wave) process. The directly measured values are the differences in frequency between the transmitted and received radar signals.

Calculations are made using signals transmitted by the ESP yaw rate sensor and the steering angle sensor as well as radar information relating to carriageway fixtures (e.g. crash barriers) and the movements of other road users. The system is integrated in the CAN network, which is present throughout the vehicle, and as a result communicates within thousandths of a second with the other control units such as the engine, transmission, and braking system.

ACC operation and displays
The driver selects his preferred speed according to the speedometer calibrations: from 30 to 80 km/h (19 to 50 mph) in increments of 5 km/h (3 mph), and above 80 km/h (50 mph) in increments of 10 km/h (6 mph). The preselected speed is shown by LEDs on the speedometer. The system’s status (on/off − vehicle identified) is also visible on the central display. The time interval between the car and the vehicle in front can be varied in four stages (from 1.0 to 2.3 seconds) and is shown graphically in the driver information system.

There are also three settings relating to the system’s dynamic character (dynamic/standard/comfort), adjustable via the MMI operating system. By accelerating or braking, the system adjusts the car’s speed until it matches the program selected by the driver.

Lane monitoring as a collision warning – Audi braking guard
The ACC sensor has an additional safety function – Audi braking guard. If there is the risk of a collision with the car in front, the system alerts the driver in two stages: first a warning tone is issued, with an optical signal appearing simultaneously in the instrument cluster. As a precaution, the ESP builds up a degree of pressure in the hydraulic system during this step, so that full braking performance is available if the driver reacts by applying the brakes.

If the driver does not react, the system rapidly builds up pressure in the braking system and a clearly noticeable warning jolt follows. This only slows the car down slightly, but is sensed by the driver as a sudden jolt and is of course intended as a ‘wake-up’ reminder. By means of extensive testing, Audi has confirmed that this is a highly effective warning signal. If the driver now applies the brakes, full stopping power is available without delay, and even hesitant pressure on the pedal will cause the hydraulic brake assist (HBA) to make a full brake application.

Audi braking guard remains active even if ACC is deactivated. Conversely, both the preliminary warning and the entire braking guard function can be switched off separately via the MMI – true to the Audi philosophy of giving the driver as much control as he wants.

A sidelong glance to the rear: Audi side assist
Audi side assist also makes use of intelligent radar technology. The system is designed to warn drivers of dangerous situations when changing lanes. Two radar sensors in the rear bumper, which operate at a frequency of 24 GHz, monitor the area alongside and behind the car to a width of up to 50 meters (55 yards). A high-speed computer analyzes the data.

Any time another vehicle traveling at roughly the same speed moves into the blind spot or a vehicle approaches rapidly from behind, a yellow LED display lights up in the housing of either the left or right exterior mirror and remains lit. This warning signal is designed to be unobtrusive so as not to distract the driver’s attention – the driver cannot see it unless he looks directly in the mirror.

The LEDs brighten and begin flashing rapidly for roughly one second if, despite the initial warning signal, the driver signals a lane change. A series of tests conducted by Audi has shown that this flashing light is nearly impossible to overlook, because the human eye is extremely sensitive to changes in contrast in our peripheral vision.

The visual display is located on the inner surface of the mirror housing so that the driver is virtually the only one who can see it. The brightness of the display adapts to the surrounding light and can also be adjusted from the MMI operating terminal. The system is activated at speeds greater than 60 km/h (37 mph) and can be deactivated by pressing a button.

Audi lane assist: Lane-changing without risk
A further high-tech assistance system from the luxury class is Audi lane assist. Above a speed of approx. 65 km/h (40 mph), it warns the driver against an unintentional lane-change. A small black-and-white camera located above the interior mirror on the windscreen monitors the road in front of the car. The lens of this camera is designed to cover a distance of 60 meters (66 yards) and a spread of 40 degrees. A powerful computer detects lane markings and prescribes the position of the vehicle with respect to these.

Any time the driver approaches one of these lines without signaling, Audi lane assist sends a warning vibration to the steering wheel. The intensity of the vibrations and the point at which they are activated can be configured at one of three levels via the MMI. Audi lane assist can also be deactivated. If the lane markings are difficult to detect, a display in the instrument cluster will indicate that the system has been activated but is not yet ready.

The APS systems: Parking made easy
Audi offers parking assistance systems that make parking child’s play. The best known of these is the proven Audi parking system (APS), which supplies an audible signal as the rear of the car approaches an obstruction while backing up. APS plus comes with front and rear visual displays, as well as eight ultrasonic sensors in the bumpers.

With its integrated rearview camera, Audi parking system advanced is the high-tech solution. The camera is built into the trunk lid and is extremely sensitive to light. It has a fisheye lens and, with its 130-degree monitoring angle, scans a broad area. Its images are processed to eliminate distortion before being displayed on the monitor of the MMI operating system.

The display includes various reference lines and zones to help the driver position the car correctly. If applicable, the camera picture also displays an optional towing bracket – allowing the vehicle to be maneuvered precisely while taking account of the trailer towing bar. In addition to this real-image mode, APS advanced also provides the classic visual and audible parking aid functions using signals from ultrasonic sensors.