Dramatic e-tron concept stuns Frankfurt show
Audi has revealed the e-tron, a high-performance sports car concept with a purely electric drive system at the Frankfurt Motor Show today. The register of interest is now available to customers via audi.co.uk or by visiting an Audi Centre.
Four motors – two each at the front and rear axles – drive the wheels, making the concept car a true quattro. The e-tron produces 230 kW and 4,500 Nm of torque, and accelerates from 0 to 60 mph in 4.8 seconds. The lithium-ion battery provides a useable energy content of 42.4 kwh, which allows the e-tron to cover around 154 miles on one charge.
The e-tron’s design proves that an electric car can compete with conventional petrol and diesel sports cars. The battery sits directly behind the passenger cabin to give it the optimal centre of gravity and axle load distribution.
The concept
Electric drive systems are significantly more efficient than combustion engines, making them better for the environment and cheaper to run. They can also be very sporty because all of the torque is available the moment the driver steps on the accelerator, giving breathtaking acceleration.
The greatest challenge of getting a concept ready for large scale production is the integration of the energy storage system. Acceptable range and performance requires a traction battery that is heavy and takes up a lot of space. Audi is taking a new, holistic approach, with a specific vehicle package, a systematic lightweight construction concept and an optimal configuration of all components for the electric drive.
The holistic approach
Lithium-ion cells are being developed for use in cars to reduce weight and increase capacity and performance. Audi will use lithium-ion technology in a hybrid production vehicle, such as the upcoming Q5 hybrid, and in the e-tron concept.
The brief for the e-tron concept goes far beyond battery technology and the replacement of the combustion engine with an electric drive system, however. Audi’s development engineers decided to design nearly every component based on the new requirements of electric mobility. This integrated approach means that the e-tron’s efficiency, range and practicality are ground-breaking.
The Audi team focused on:
The reduction of road resistances to increase the vehicle’s range. Lightweight construction was a top priority for the e-tron concept car. The body, in particular, combines low weight with supreme strength and rigidity. An intelligent aerodynamics concept with active elements helps to reduce energy consumption
• The safe integration of the electric drive system and the battery. Placing the battery in front of the rear axle ensures an optimal axle load distribution without compromising the overall design and the generous amount of interior space
• Advanced battery technology that enables a practical range and has a long service life. The battery system is water-cooled for optimal performance and service life
• A needs-based energy management system to control all functions for the chassis, convenience equipment and other auxiliary consumers
• An innovative thermal management system with matched cooling and heating components considers the cooling requirements of the battery and the drive system in addition to the interior temperature
• Driving dynamics and road comfort are what Audi customers have come to expect in the sports car segment
• Vehicle safety is on par with the best of today’s production vehicles
• Clear and comprehensive information for the driver
The e-tron concept car uses car-to-x communication technology developed by Audi to improve the efficiency of conventionally powered vehicles. For example, information about traffic light cycle times and the flow of traffic – provided by the infrastructure and other vehicles – is used to compute an optimal driving strategy. Audi has already modelled such a solution in Ingolstadt as part of its “travolution” project.
Design and package
High-efficiency LED technology is used for all lighting units on the e-tron. The headlamps are the core of a fully automatic light assistance system that reacts flexibly to any situation. The new technology recognises weather conditions and adapts the illumination to rain or fog. The technology at the heart of the light assistance system is a camera that works with a fast computer to detect oncoming traffic, recognise lanes and measure visibility.
If there is oncoming traffic, for example, the high beams are turned off in the corresponding section of the illumination field. The cornering light system analyses data from the navigation system and illuminates corners before the driver steers into them. The Audi e-tron does not have conventional fog lamps that consume additional power. It instead intelligently varies the low beams to widen the illumination field, thus significantly reducing the glare from the car’s own lights. The variability of the headlamps is also reflected in their design. The LED elements change the appearance and the character of the front end of the vehicle depending on the speed driven and the ambient conditions.
A new design element unique to the e-tron are the air intakes in the single-frame grille and in front of the rear wheel wells. They are closed flush under normal circumstances and opened by means of flaps when additional air is needed for cooling. The flaps are kept closed when not in use so that the concept car has a remarkably low drag coefficient.
The vehicle body is compact. The sweeping line of the front end and the flat curved roof immediately identify the two-seater as an Audi. The contours of the flanks are familiar. The tapering of the dynamic line above the sill and the shoulder line tie together the front end, the side and the rear, lend a plastic quality to the doors and the transition to the side air intake and sharply emphasize the Audi-typical round wheel wells with the large, 19-inch tyres.
At 1.90 m wide, 4.26 m long and 1.23 m tall, the e-tron has the proportions of a supercar. The wheelbase of 2.60 m leaves plenty of room between the axles for people and technology. Like with a mid-engined sports car, the cabin of the e-tron is shifted far forward toward the front axle, leaving room in front of the rear axle for the roughly 470 kg battery unit, the inverter and the power electronics.
The two electric motors, which have their own cooling system, are mounted behind the rear axle. The front electric motors are mounted on the front axle, with their cooling system arranged in front of them. This special package, which features a 42:58 weight distribution, ensures perfect balance, which contributes to the driving dynamics of the e-tron.
Systematic lightweight construction is an important prerequisite for efficiency and range with electric vehicles than for conventionally powered automobiles. The body structure is based on Audi Space Frame (ASF) technology. All add-on parts – doors, covers, sidewalls and roof – are made of a fibre-reinforced plastic.
The combination of aluminium and carbon fibre-reinforced composite material guarantees supreme rigidity coupled with low weight. Audi will use this technology in a similar form for production vehicles. Despite the complex drive system layout with four electric motors and a high-capacity battery system, the total weight of the Audi e-tron is only around 1,600 kg.
Interior and control concept
Optical and functional references to the new drive concept characterise the interior design. They establish an advanced connection between proven Audi genes and new formal hallmarks. Typical for the Audi design language is the reduction of the architecture, controls and flow of information to the essential in favour of visible lightweight construction and a tidy overall impression.
The dash appears to float and has a curve that extends laterally into the door panels. With no need to allow for a transmission, shifter and cardan tunnel, the designers took advantage of the opportunity to create a particularly slim and lightweight centre tunnel and centre console. The flush gear selector, with which the driver chooses between the modes forward, reverse and neutral, emerges from the tunnel when the vehicle is started.
The cockpit of the e-tron is also oriented toward the driver – another characteristic Audi trait. Instead of the classic instrument cluster, the concept car is the first Audi to be equipped with a large, fold-out central display with integrated MMI functions. The MMI is controlled via a scroll pad with a touch-sensitive surface on the steering wheel (“MMI touch”) – an element inspired by modern smartphones.
While an analog speedometer on the right provides speed information, the instrument on the left tells the driver how much power is being drawn. The central display shows the range in the status bar and presents all key information from the infotainment and navigation systems. It also provides the driver with relevant data from the vehicle’s communication with its surroundings. The instruments combine the analog and the digital worlds into a single unit.
Characteristic for the concept of the Audi e-tron is the near total elimination of switches and small components such as the ignition. The climate control unit is located to the right above the steering wheel. The display provides temperature and ventilation information. Again drawing inspiration from a smartphone, the system is controlled by means of a touch-sensitive sliding control.
The racing-inspired lightweight bucket seats combine excellent lateral support with comfort. Two contrasting colours – snow white and cognac – delineate the various zones of the interior. The colours and the high-quality materials combine elegance and sportiness.
Drive system and energy supply
Four asynchronous motors with a total output of 230 kw give the Audi e-tron the performance of a high-output sports car. The concept car can accelerate from 0 to 60 mph in 4.8 seconds. The torque flows selectively to the wheels based on the driving situation and the condition of the road surface, resulting in outstanding traction and handling.
The top speed is limited to 124.27 mph because the amount of energy required by the electric motors increases disproportionately to speed. The range in the NECD combined cycle is around 154 miles. This is made possible by the integrated concept: technology specially configured for the electric drive system combined with state-of-the-art battery technology. The battery block has a total energy content of roughly 53 kwh, with the usable portion restricted to 42.4 kwh to increase service life.
The energy storage unit is charged with household current (230 volts, 16 amperes) via a cable and a plug. The socket is behind a cover at the back of the car. With the battery fully discharged, the charging time is between six and eight hours. A high voltage (400 volts, 63 amperes) reduces this to around 2.5 hours. Audi engineers are working on a wireless solution to make charging more convenient. The inductive charging station, which can be placed in the garage at home or in special parking garages, is activated automatically when the vehicle is docked. Such technology is already used today in a similar form to charge electric toothbrushes.
The battery is charged not only when the car is stationary, but also when it is in motion. This form of energy recovery and return to the battery is already available today in a number of Audi production models. During braking, the alternator converts the kinetic energy into electrical energy, which it then feeds into the onboard electrical system.
The Audi e-tron is slowed by an electronic braking system of four lightweight ceramic brake discs. The electronic braking system makes it possible to tap into the recuperation potential of the electric motors. A hydraulic fixed-caliper brake is mounted on the front axle, with two electrically-actuated floating-caliper brakes mounted on the rear axle. These floating calipers are actuated not by any mechanical or hydraulic transfer elements, but rather by wire (“brake by wire”). This eliminates frictional losses caused by residual slip when the brakes are not being applied.
This decoupling of the brake pedal enables the e-tron’s electric motors to convert all of the braking energy into electricity and recover it. The electromechanical brake system is only activated if greater deceleration is required. These control actions are unnoticeable to the driver, who feels only a predictable and constant pedal feel as with a hydraulic brake system.
The heat pump
The heat pump – used here for the first time ever in a car – also increases efficiency and range. Unlike a combustion engine, the electric drive system may not produce enough waste heat under all operating conditions to effectively heat the interior. Other electric vehicles are equipped with electric supplemental heaters, which consume a relatively large amount of energy. The heat pump used by Audi – and commonly used in buildings – is a highly efficient machine that uses mechanical work to provide heat with a minimal energy.
A high-efficiency climate control system is used to cool the interior. It works together with the thermal management system which also controls the temperature of the high-voltage battery. The battery, the power electronics and the electric motors must be kept at their respective ideal operating temperatures to achieve optimal performance and range.
As soon as the vehicle is connected to a charging station, it is preconditioned as appropriate by the thermal management and other associated systems.
The drive system is heated if temperatures are cool, and cooled if hot. This preconditioning can be extended to the interior so that passengers can step into a cabin that has been heated or cooled for their comfort.
Driving dynamics
The normal distribution of tractive power is clearly biased toward the rear axle in accordance with the weight distribution of the e-tron. Similarly to a mid-engined sports car, roughly 70 percent of the power goes the rear and 30 percent to the front. If an axle slips, this balance can be varied by the four centrally controlled electric motors.
The four individual motors, which are installed behind the wheels as wheel drives to give greater traction, also enable the e-tron’s lateral dynamics to be intelligently controlled. The targeted acceleration of individual wheels (torque vectoring) – makes the e-tron even more dynamic while simultaneously enhancing driving safety. Understeer and oversteer can be corrected by the targeted activation of the brakes and by precise increases in power lasting just a few milliseconds. The concept car remains extremely neutral even under great lateral acceleration and handles superbly through corners.
The chassis has triangular double wishbones at the front axle and trapezoidal wishbones made of forged aluminum components at the rear axle – a geometry that is a prerequisite for high agility, uncompromising precision and precisely defined self-steering behavior.
The direct rack-and-pinion steering gives finely differentiated feedback. Its electromechanical steering boost varies with speed, so that the e-tron only has to provide energy while steering, and not while driving straight ahead.
The e-tron concept car rolls on 19-inch tiyes with a new blade design. 235/35 tyres up front and 295/30 tyres at the back provide the necessary grip.
Car-to-x communication
The electronics development engineers at Audi aimed to make the e-tron as efficient and fun to drive as possible, while being concerned with safety and traffic management. The technical concept car includes a prototype of an information processing system. Future generations of these systems will usher in a new era in the networking of road traffic, particularly in regions and countries with high volumes of traffic. This progress is made possible by the rapid advancements in computing power, software and communication technology.
The buzzword ‚car-to-x communication’ refers to the direct exchange of information in flowing traffic and to the traffic environment. The letter ‘x’ is a free variable that can refer just as easily to other vehicles as to fixed infrastructure such as traffic lights. In contrast to today’s telematic systems, car-to-x communication does not require a central service provider to quickly and effectively pool and process information. The participants perform these tasks by spontaneously networking with one another.
The future car-to-x network needs further development before it becomes reality on the roads. However, nearly every carmaker in Europe, the USA. and Japan has decided to develop a common standard for hardware and software to ensure compatability. Once all new cars are equipped with this technology, a functional network of automotive transmitters will be available in large population centres. This will provide information about accidents from vehicles involved in the accident (eg location), traffic flow information and car parking information.
