New Powertrain Integration Centre (AIZ): State-of-the-art test rigs

Oct 28, 2016
Stuttgart/Sindelfingen

With its new Powertrain Integration Centre (AIZ), in summer 2016 Mercedes-Benz took into service one of the automotive industry's most advanced test facilities. A total of ten vehicle test rigs inside an all-new state-of-the-art building in Sindelfingen are used for such purposes as the fine tuning of engine and transmission – comfort, dynamics and agility are matched to each other. The highlights include test rigs with high-precision torque measurement directly at the wheels of the vehicle as well as a test rig with a climatic altitude chamber, which uses partial vacuum to simulate an altitude of up to 5000 metres at temperatures of down to -30°C, while the vehicle operates fully automatically on a chassis dynamometer.

The powertrain is the heart of an automobile. It determines the vehicle's dynamics and efficiency. The fine tuning of powertrain components is one of the typical tasks that, since summer this year, have been carried out by the vehicle developers at Mercedes-Benz at the new Powertrain Integration Centre. The vehicles are tuned for comfort and agility in situations such as load change, kick-down or motor cut-in in hybrid vehicles. The AIZ is also where our developers calibrate the DYNAMIC SELECT transmission modes, which are now available in many Mercedes-Benz models.

The primary task of Electronic Engine Management is the coordination of all signals, with the goal of guaranteeing that engine operation is as economical as possible, yet also dynamic, comfortable and trouble-free - together with the minimum possible emissions. The term "application" describes the matching of a basic engine to the specific characteristics of the vehicle model in question as well as to the often highly different requirements of the various markets.

The control unit processes the incoming sensor/control information and computes closed-loop control signals for the individual components. Depending on the engine, the following are among the parameters that are controlled: ignition timing, injected fuel quantity, injection timing, exhaust gas recirculation, throttle valve position, variable-geometry intake manifold setting, variable turbine geometry (on turbocharger) and camshaft adjustment. Added to this is suitable control of the transmission and all-wheel drive as well as of driver assistance systems, such as ESP®.

On top of this system diversity, the number of variants is increased through the development of alternative drive systems. There is therefore a growing need for testing on test rigs – the validation of all variants on the road under all climatic conditions would be a challenge from the point of view of time. Reproducible test conditions are important for being able to precisely measure the influence of each parameter. This is where the AIZ comes in.

98 percent of braking energy is recovered

The new building at the Sindelfingen Mercedes-Benz Technology Centre (MTC) houses ten vehicle test rigs for tuning vehicles and their powertrains. The new building used 16,800 m3 of concrete, equivalent to the capacity of five Olympic swimming pools. There were also 2500 tonnes of reinforcing steel. The designers of the AIZ attached great importance to systematic energy recovery, with 98 percent of the electric braking energy produced on the test rigs being fed back into the power network. Also, the air conditioning of the test rigs is energy-neutral for two-thirds of the year, which means that no power is consumed from the joint network. With all ten test rigs in continuous operation, this would be the same as supplying around 7500 households with electricity.

Special wheel hubs with through-drive to high-power asynchronous machine

Among the state-of-the-art test rigs, the vehicle powertrain test rig stands out as technologically especially sophisticated: the vehicle does not run on a roller as usual, but is connected at each wheel by special wheel hubs directly to a high-power asynchronous machine via a precision torque-measuring system. This simulates the driving resistances as well as realistic road conditions – including under critical conditions. Each electric machine has an output of 270 kW and up to 4000 Nm of torque per wheel. The vehicle components are suitably cooled by an airstream blower, which blows out air at up to 180 km/h. This allows for highly dynamic driving manoeuvres with which the overall vehicle can be ideally parametrised, including for extreme situations.

Climatic altitude chamber simulates driving at 5000 metres

Another feature of the AIZ is a chassis dynamometer with an especially effective climatic altitude chamber, in which the powertrain can be tested in a complete vehicle. This simulates the particular climatic conditions to which an engine is subjected when in the mountains. At altitude, air contains less oxygen, which means that correspondingly less fuel can be burned. The test rig is also capable of simulating temperatures of down to -30°C.

To simulate altitude, the air is pumped out of the chamber under partial vacuum. It is possible to simulate 250 metres of altitude difference per minute, the maximum altitude being 5000 metres. At this extreme negative pressure, there is a weight of around 50 tonnes on the three by three metre gate to the entry point through which the vehicles are brought to the test rigs. There are therefore unmistakable parallels with a safe: the gate is made of solid steel and is 25 centimetres thick.

Automated testing round the clock

There are two other chassis dynamometers in climatic chambers. These can simulate temperatures between -30°C and +42°C. Just as in the altitude chamber, test drivers cannot be expected to work on the test rigs. The test rigs are therefore highly automated: the vehicles are electronically activated, accelerating and decelerating as if by magic or changing the gears of the transmission.

As the engineers and technicians are not in the car, but outside at the control console, they can also simultaneously evaluate measurements using newly developed tools. Furthermore, state-of-the-art automation technology with automatic test sequence control and monitoring allows unmanned round-the-clock operation of the AIZ. This also requires an automatic refuelling system.

The key facts about the new AIZ:

  • Constructed: 2014 to 2016
  • Employees: approximately 50
  • Building dimensions (length/width/height): 123.5/36/28 metres
  • Total of ten test rigs
    • Three vehicle powertrain test rigs
    • Three application chassis dynamometers
    • Four exhaust test rigs
  • Automatic parking storage system for 82 vehicles
  • 16 cold chamber spaces for pre-cooling of vehicles prior to climatic chamber tests
  • Two cold start chambers

Extension of the Mercedes-Benz Technology Centre

The new Powertrain Integration Centre is part of extensive additions and conversions to the Mercedes-Benz Technology Centre (MTC) in Sindelfingen. The new driving simulator, climatic wind tunnels and a high-tech aero-acoustic wind tunnel are already in operation. By 2018, there will also be a state-of-the-art technology centre for vehicle safety, an electronics testing centre and a computer centre. Housed on the upper floor of the AIZ, the computer centre will directly use the electricity generated downstairs on the test rigs in order to operate and cool the computers.

The MTC is home to the headquarters of the company's global Group Research and passenger car development, including design.

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