Virtual development

Audi Magazine: Your simulator was the first dynamic one in the whole group. What was your reasoning for purchasing it?

Richard Uhlmann: My team is part of the Advance Vehicle Development function. We work on the characteristics of future vehicle models at the very earliest phase of the development process. The dynamic driving simulator was installed in 2014 and enables us to provide extremely good handling predictions and to support the decision-making process before the first expensive prototypes are built.

Can you simulate all Audi models from the A1 to the Q7?

Richard Uhlmann: Yes, we can simulate the entire vehicle lineup – from a vehicle with basic equipment all the way through to one with wide-ranging chassis control systems and electric drive. We use the simulator to address aspects of developing ride and handling. One example is wheels and tyres, which have a major influence on vehicle stability in high-speed avoidance manoeuvres. We can carry out this kind of testing using the driving simulator without any risk at all. Our colleagues working on the development of assistance systems and piloted driving are also interested in our simulator.
Can you briefly explain the technology to us?

Richard Uhlmann: The entire system was developed in close co-operation with a specialist company. The motion system is a so-called hexapod, which consists of six electromechanically powered telescopic cylinders. They carry a frame onto which half of the occupant cell of an Audi A6 is fixed. Each cylinder can travel 64 centimetres in and out extremely quickly, giving the cell a wide range of movement. It tilts to the side when simulating cornering, forwards under heavy braking and oscillates up and down when driving over bumps in the road. Compared with a static simulator, the additional movement available lowers the risk of motion sickness. And one very important aspect is that the simulated movement is fully synchronised with the image presented on the screen.

How does the simulation work on a visual level?

Richard Uhlmann: We have seven LED full HD beamers which project the virtual world onto a cylindrical screen. It’s around eight metres in diameter, four metres high and surrounds the hexapod for 200 degrees. Each beamer is fed by its own dedicated rendering PC.

This means you are fully immersed in the scenery – but how realistic is the sensation of driving?

Richard Uhlmann: Our driving simulator can recreate some driving characteristics extremely well. They include the low-frequency vertical oscillations caused by driving along a bumpy road, dynamic stability, the necessary steering angle and the forces at the steering wheel, which are generated by a dedicated electric motor. For some of the other aspects, we have to turn to our box of tricks. By way of example: A modern vehicle has a braking distance of around 36 metres from 100km/h. If the braking process is to feel exactly as it does in reality, you would have to move the occupant cell 36 metres backward during braking. This would need an awful lot of space, which we don’t have. So, we’ve developed an electronic belt tensioner that tightens proportionally with braking force. This synthesised signal helps provide the driver with an approximation of the braking process that is as realistic as possible.

So, the more of the driver’s senses it incorporates, the more realistic the simulation feels …

Richard Uhlmann: That’s correct in principle. But, the different stimuli have to be good and also in tune with one another in a way that makes sense. The technical term for this is “motion cueing”. We developed what we call “Audi Motion Cueing” as part of a dissertation. It serves all the senses that are in play while driving, including hearing. For instance, the tyres screech more loudly the faster you drive around a corner.

Can you use the simulator to assess tyre characteristics?

Richard Uhlmann: We can for certain specific tyre characteristics. Audi test drivers are incredibly astute professionals. For example, we let them drive with several different virtual tyres in a blind test – meaning the drivers don’t know the specific tyre characteristics. They assess the overall vehicle behaviour and, based on that, can draw conclusions on the tyres. So, the drivers can tell whether they are running on a soft or a harder tyre. This means that deviations can be evaluated with a certain degree of repeatability.
You’re showing an autobahn simulation at the moment, but what other kinds of roads can you simulate with the unit?

Richard Uhlmann: The autobahn simulation is really interesting actually, because it involves a slalom and a double lane change. We’ve also digitised some sections of our Audi proving grounds. Plus, there’s a city setup and, something of a highlight, the Zandvoort race track …
... and which of you has the best lap time in Zandvoort?

Richard Uhlmann: Ah, that’s a secret (laughs)! But I can tell you this much – right now, it stands at 1:28.541. We reconfigured the simulator for an Audi race car with WEC technology to do that. The time is just nine seconds slower than the record set by Max Verstappen in his Formula 1 race car.