Audi is showcasing an electric off-roader concept at IAA 2019: the Audi AI:TRAIL quattro. The AI: TRAIL joins the other three exploratory use case vehicles—the Audi Aicon, AI:ME, and AI:RACE—on Audi’s stand.
The performance specifications for the Audi AI:TRAIL are markedly different from those for conventional automobiles, because the car’s development was not about achieving remarkably quick acceleration or hitting breathtaking speeds on the highway.
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 kilometers (248.5 to 310.7 mi) 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 kilometers (155.3 mi).
In order to meet these requirements, the vehicle is designed to reach a maximum speed of 130 km/h (80.8 mph) 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 kW and the maximum torque is 1,000 N·m (737.6 lb-ft). 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.
With an exterior length of 4.15 meters (13.5 ft) and a width of 2.15 meters (7.05 ft), the brawny Audi AI:TRAIL’s potential away from paved roads is immediately apparent. The roof height of 1.67 meters (5.5 ft) and the enormous 22-inch wheels with 850 mm (33.5 in) tires hint at the vehicle’s excellent off-road capabilities even when it is standing still. With a ground clearance of 34 centimeters (13.4 in), it can ford through water more than half a meter (1.6 ft) 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—and one that indicates the vehicle’s kinship with Aicon and AI:ME—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.
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 (3,858.09 lb) despite its high-capacity battery.
Bulky transverse links and MacPherson suspension struts with coil springs and adaptive dampers provide suitable robustness and ensure safe driving stability. The special tire 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 tires themselves—in addition to the suspension struts—to contribute a further 60 millimeters (2.4 inches) of suspension travel. Aside from improved off-road capability, this provides the occupants with an enormous amount of additional comfort.
The tires 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 tires accordingly. As regards traction, it can be useful to reduce the pressure, such as when driving on sand, and thereby increase the tire contact patch. By the same token, increasing the pressure again when switching to asphalt increases drive stability.
Lights and drones. 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.
When the AI:TRAIL is stationary, the drones can also illuminate the surrounding area from their position on the roof; for example, when the occupants are enjoying a picnic next to the vehicle. They can also illuminate the interior through the transparent panoramic roof if the occupants prefer to remain inside the vehicle.
The drones, which are coordinated fully automatically by the AI:TRAIL, usually fly at least in pairs. If necessary, they can also provide additional light intensity or illuminate the area around the vehicle by coming together to form groups of up to five drones. The occupants can simply use control software on their smartphones to set their desired scenario.
The Audi Light Companion is just as easy to use. This is a light source that is shaped like a large flashlight but has a much more extensive range of functions. It is normally magnetically attached to the front side of the seat, where it acts as ambient lighting. However, you can also take the Light Companion with you when you leave the AI:TRAIL, and this is when it really shows what it can do. Integrated in its housing are three legs that can be used to stand the light in place and turn it into a campfire light or a close-range floodlight. The housing also accommodates several cameras that can scan the way ahead or take videos of the scenery, which can then be uploaded directly so social media.
However, that is not the end of the Audi Light Companion’s talents. When integrated with the AI:TRAIL’s navigation system, it is capable of projecting directional symbols and even written information onto a route and thereby helping AI:TRAIL users to find their way around when hiking.
Automated driving. The Audi AI:TRAIL is designed for driving on roads up to level 4. Level 4 is the second-highest level on a standardized 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.
The driver will need them when going off road at the latest. After all, although even unpaved dirt tracks and forest paths have been mapped extensively through digital cartography, the way in which their surfaces frequently erode makes them too variable to allow their limits and any damage to be digitalized for automated driving reliably and for any extended period. Automated driving in the reduced-speed level 3 range can therefore be possible on dirt roads only in exceptional cases and at low speeds. In these situations, the driver will have several seconds to take over.
But the sensors and assist systems don’t leave the driver of the AI:TRAIL alone, even off-road. First of all, there is the tried and tested sensor system for the ESP on board. The data for friction values and slip, longitudinal and lateral acceleration provide the electronics with all necessary parameters they need in order to optimize drive stability. There is also a whole range of sensors that can detect both the road surface and obstacles; they work with optical systems such as cameras and lasers, as well as with ultrasound and radar. The data that they provide enables the central driver assistance system to avoid collisions by intervening with the steering and braking as needed.
The electronics also assist the driver with conquering uneven stretches; for example. when the vehicle is in a tilted position or on particularly challenging inclines. Where necessary, the systems warn the driver when critical limits are about to be exceeded, such as ground clearance or angles of incidence that are difficult to control. They can also keep the vehicle on track, within the limits of the system—much like a lane-keeping assist working in concert with cruise control. Depending on the circumstances, this puts the vehicle at automation level 2. However, it requires the driver to be paying attention at all times. The smart assistance systems do provide effective support, definitely help to improve safety and take a significant amount of the strain off the driver.