Audi debuts AI:TRAIL quattro, an Off-Roader of the Future

Audi showcased an electric off-roader for the future of road transport: the Audi AI:TRAIL quattro, a comprehensive concept for sustainable mobility off the beaten track at the IAA 2019.

The four-seater Audi AI:TRAIL quattro combines the capacity for automated driving with superb off-road capabilities. The glass surrounding the cabin extends all the way to ground level, providing unrivaled all-round visibility. The ample battery capacity ensures sufficient range even away from dense networks of charging stations.

The “Trail” part of the name evokes the idea of exploring nature. That is why there are no big screens on board for streaming TV series or videoconferencing; instead, broad glass surfaces provide a clear view of the surroundings. This is how Marc Lichte, Audi's Head of Design, described the use case: “With the AI:TRAIL, we are showing an off-road concept with an emissions-free electric drive for an innovative driving experience away from paved roads. Consistent with this, we designed a monolithic basic vehicle body with maximum glazing to create an intense connection to the surroundings. A concept for sustainable mobility on demand.”

The Audi AI:TRAIL quattro is the fourth entrant in the series of concept cars with electric drive systems, which began with the presentation of the Audi Aicon at the 2017 iteration of the IAA. Following this luxury-class vehicle very much intended for highly automated long-distance driving, an emissions-free monoposto designed for the race track, the Audi PB18 e-tron, made its debut in Pebble Beach in 2018. It has been given a new name in time for IAA 2019, gaining the shared “AI” prefix to indicate that it, too, is part of the family. It is now known as the AI:RACE, which leaves no illusions as to the purpose of the electric sports car.

The third in the series, the Audi AI:ME—introduced at the 2019 Auto Shanghai show—is an autonomous city car aimed at megacities all over the world. It allows its passengers to stop worrying about the stop-and-go traffic that is inevitable in urban areas, offering them perfect connectivity and a comprehensive range of infotainment services, helping them to spend their time in the vehicle as usefully and as relaxed as possible.

Finally, with the AI:TRAIL, Audi is now opening up the potential applications for its visionary vehicles to include off-road terrain. The car is equipped with four electric motors, systems for assisted and automated driving and—typically for Audi—quattro permanent all-wheel drive.

With an exterior length of 4.15 metres and a width of 2.15 meters, the brawny Audi AI:TRAIL's potential away from paved roads is immediately apparent. The roof height of 1.67 meters and the enormous 22-inch wheels with 850 mm tyres hint at the vehicle's excellent off-road capabilities even when it is standing still. With a ground clearance of an impressive 34 centimetres, it can ford through water more than half a metre deep. On rough, rocky terrain, this architecture provides plenty of agility without the battery unit integrated in the floor coming into contact with the ground.

The cabin itself is an extensively glazed space surrounded by polygonal shapes, with room for up to four people. One characteristic feature is the protruding ridge halfway up the side windows. This line continues to both the front and rear and acts as a waistline uniting the entire body in one monolithic whole. With the electric drive system arranged around the axles and the battery in the floor, there is no need for overhanging sections or separate attachments for the motor or batteries. Something else that the four visionary Audi vehicles at IAA 2019 will be demonstrating is that the one-box design is becoming the gold standard for the age of the electric vehicle.

Light weight and maximum body stiffness are, of course, important technical objectives for off-roaders in particular. That is why the body of the Audi AI:TRAIL is made of a mixture of high-tech steel, aluminum and carbon fiber. As a result, it weighs just 1,750 kilograms despite its high-capacity battery.

In the interior, the side window ridges give passengers space where they objectively need it the most—around their shoulders and elbows. They also provide extra space where they subjectively perceive it most acutely, as the way in which the side windows extend down low opens up a clear down to the ground, even between the wheels. The aim of the designers here was to give those inside the vehicle the best possible view of nature and their surroundings, breaking the boundaries between the interior and the world outside.

The windshield wraps around the front of the vehicle like the cockpit of a helicopter. Passengers have an unobstructed view of the road or trail both in front and to the sides. Nor is it just the front and sides that are transparent and covered in glass. Almost the entire roof, from the top of the windshield to the rear spoiler, allows a clear view of the sky and the landscape. Even the vertical Singleframe is glazed, with only the four rings of the badge sitting in their customary position in what is otherwise a glass octagon.

Bulky transverse links and MacPherson suspension struts with coil springs and adaptive dampers provide suitable robustness and ensure safe driving stability. The special tyre design becomes apparent at first glance, as the profile appears to be drawn all the way up into the high tire sidewalls. However, behind it lies a structure of supporting struts, which are integrated in the treads, and the actual surface. This design allows the tyres themselves—in addition to the suspension struts—to contribute a further 60 millimetres of suspension travel. Aside from improved off-road capability, this provides the occupants with an enormous amount of additional comfort.

The tyres also feature variable, sensor-controlled air pressure regulation. Optical sensors and electronic stability control (ESC) work together to detect the condition of the road surface and adjust the air pressure in the tyres accordingly. As regards traction, it can be useful to reduce the pressure, such as when driving on sand, and thereby increase the tyre contact patch. By the same token, increasing the pressure again when switching to asphalt increases drive stability.

The interior of the Audi AI:TRAIL is tidy and spacious, and it has just a few visible control elements. There are two comfortable-looking, almost delicate seat shells in the front row, both equipped with four-point seat belts. Light colors dominate the upper interior area down to the level of the seat cushion and the low dashboard. The openness to the outside world appears all the more present; the occupant's eye is drawn to the large glass areas in the front and side sections and guided through the almost fully glazed roof.

Pedals, a yoke for a steering wheel, a few buttons, and a smartphone attached to the steering column as a display and control centre for vehicle functions and navigation—those are all the elements there are for the interaction between the driver and the vehicle.

The second row features a novelty in the form of two seats designed like hammocks. When taut and tensioned in a transportable tubular frame, panels of fabric form a comfortable seating surface and backrest, and the backrest that is drawn around to the side even provides lateral support. These seats are good for relaxation in more ways than one, as they can even be taken out of the AI:TRAIL and used as mobile outdoor chairs.

Instead of conventional headlights, self-contained light sources sit below the A-pillars and can shine both outward and inward. These LED elements are dimmable and adjustable and can be used as interior lighting as well as for lighting the vehicle's path. The rear light operates in a similar way. Extending across the full width of the rear section, this element can be used to illuminate the luggage compartment and as distinctive signature lighting for the exterior.

Instead of conventional low beams and high beams, the Audi AI:TRAIL is equipped with a total of five rotorless, triangular, electrically operated drones with integrated matrix LED elements. They are capable of landing on a roof rack or directly on the roof of the vehicle, and docking onto the inductive charging elements.

The flying objects are Audi Light Pathfinders, which generate their lift in the same way as bladeless fans produce their air flow. Thanks to their markedly lightweight design, they can fly ahead of the AI:TRAIL, consuming comparably little energy in the process, and illuminate the path ahead, thereby replacing headlights entirely. If desired, the on-board cameras generate a video image that can be transmitted to the display in front of the driver via Wi-Fi, turning the Pathfinders into eyes in the sky.

Audi AI is the code for a variety of electronic systems that relieve strain on drivers and simultaneously offer them new ways to use the time spent in the car. To this end, Audi AI also uses strategies and technologies from the field of artificial intelligence and machine learning. Audi AI combines vehicle intelligence, which makes automated driving possible in the first place, and interaction intelligence, which turns the vehicle into the occupants' partner.

The Audi AI:TRAIL is designed for driving on roads up to level 4. Level 4 is the second-highest level on a standardised international scale for increasing automation. Although systems in this category do not require any assistance on the part of the driver, their function is limited to a specific area—such as highways or areas of inner cities equipped with suitable infrastructure. In these places, the driver can completely transfer the task of driving to the system. The driver needs to resume the task only when the car leaves the area defined for fully automated driving. The Audi AI:TRAIL is therefore equipped with the traditional steering wheel and pedals.

Given that the AI:TRAIL is intended for use in areas without charging infrastructure, the thing that really draws the attention is its range. The stated target with its lithium-ion battery is 400 to 500 kilometres on roads or easy off-road terrain (in line with the WLTP). On rough ground, where the almost constantly elevated wheel slip alone means that energy consumption is higher, the limit is still an impressive 250 kilometres.

In order to meet these requirements, the vehicle is designed to reach a maximum speed of 130 km/h on the road. The vehicle electronics continuously monitor the energy flow and consumption, thereby ensuring maximum economy even during off-road driving.

In terms of drive hardware, the Audi AI:TRAIL is equipped with four electric motors installed near the wheels, each of which propels one wheel directly. As is typical for Audi, the off-roader is therefore a true quattro. The maximum system output is 320 kilowatts and the maximum torque is 1,000 Newton-metres. Usually only a fraction of this power is mobilized; the drive of just one axle is often sufficient.

Due to the individually propelled wheels, the vehicle can do without differentials and locks, which also consume energy. Thanks to the moderately calculated maximum speed, the gear ratio can be designed such that every wheel is provided with enough torque even without a multi-speed transmission.

The electronics coordinate driving stability and traction. If energy-consuming slip can be avoided, it reduces the supply of torque to the affected wheel. However, in situations in which slip is useful, such as on low-grip uphill stretches, the system permits it automatically. The large amounts of reserve power of the AI:TRAIL allow it to conquer challenging stretches even in difficult conditions—confidently, safely and always without emissions.