Avoiding a moose in the road at 170 km/h (106 mph) concentrates a driver’s mind wonderfully. Data to be computed in less than 1 s includes: speed, distance, road surface, visibility, other potential obstacles (oncoming traffic), an appreciation of what your vehicle can realistically be expected to achieve in the inevitable maneuver (known handling in specific conditions), and your own competence.
Now add to that the fact that you are in a very early prototype of the new Mercedes-Benz CLS with unproven suspension, steering, and brake system settings.
This could be a never-to-be-forgotten moment—but for one vital fact: the artificial moose drama (or rapid slalom/lane change) is happening in Mercedes’ new 360° moving base driving simulator, that forms a central element of a €160 million, five-year investment in expanding the company’s Sindelfingen Technology Center, which will also include climate wind tunnels. Mercedes believes that its new simulator complex is now the global leader in its sector.
“The Simulation Center is both a development tool and an innovation,” says Prof. Dr. Ludger Dragon, Head of Driving Behavior, Simulations and Analysis, Group Research and Advanced Development, for Daimler. “The facilities we use are the most modern of their kind in the world. Here, powerful computers enable us to create and calculate digital prototypes and to put them on a digital road. We have brought together five different types of simulators under one roof. Using the handling or moving-base simulator and the ride simulator, we can test the digital prototypes in many driving situations.”
Which was why this AEI editor was experiencing a moose moment. The prototype responded by feeling unwieldy, under-damped, and with a low steering ratio that could have created a crisis from a drama. Disaster—and the simulated moose—were avoided, but it had been a heartbeat-raising challenge.
Then it was time to do it again, now with a simulated production CLS; same speed, same moose, but this time it was a far more linear experience: hugely more responsive suspension and precisely weighted, higher geared steering meant that the heartbeat rates of both moose and driver were considerably lower.
It is this level of simulator-led development that Mercedes will be applying to new models now under development. Although it has used simulators for 25 years to shorten R&D time, it has had nothing as advanced as its newly installed systems, and never before have all its simulators been positioned on a single site.
“We can also exhaustively test highly complex technical innovations, including new driver assistance systems at an early stage in the development process—and entirely free of hazards or risks,” explains Dragon.
The moving base simulator has a 7.5-m (24.6-ft) dome, which can contain a real car, van, or truck cabin/cab. A realistic 360° screen visualization of the vehicle’s surroundings is via eight projectors onto the inside of the dome. Pedestrians move, trees cast shadows, intersection traffic is shown, and there is a night driving mode. A comprehensive sound system is fitted.
A 90° turntable is used to turn the vehicle body in the simulator to make use of the linear axis representing transverse or longitudinal movement, reach for which is 12.5 m (41 ft). Vehicle movements are transferred to the dome via a linear carriage and an electrical hexapod (six drive elements) to provide pitch, roll, and yaw effects and transnational motion.
The nose of the car dives under braking, and body roll is transmitted through simulated corners. Transverse and longitudinal movement is achieved with acceleration rates of up to 1 g (10 m/s² ) and at speeds of up to 10 m/s (36 km/h) enabling a double-lane-change maneuver or moose test to be realistically simulated.
Individual cylinders extend and retract to provide rotational movement. In many respects the system creates similar inputs to that of an advanced military aircraft simulator. It has a 12 m (39 ft) long rail that guides both transverse and longitudinal movement. The computer control system calculates driving characteristics of the car at a rate of more than 1000/sec.
“To execute smooth movements, the linear carriage is air-cushioned and almost floats on the guidance system, which weighs 300 t,” adds Dragon. “At 220 kN, the linear motor has a power output about twice that of a German high-speed ICE [Inter-City-Express] train. When the brakes are applied, the energy is recuperated and fed into our plant’s network.
“With this system, we are able to re-create in real time some of the actual vehicle behavior and precisely simulate very dynamic maneuvers—for example, double lane changes and slalom driving. This allows us to approach the limits of what is physically possible in driving.”
Other simulators at the Sindelfingen complex include a motion system ride system (which also contributes to chassis tuning) to test digital prototypes; together with the moving base system, it makes a very large contribution to resolving the ride/handling compromise.
Two fixed-base simulators have the same software and hardware as that of the moving-base systems. They facilitate preparation for first test drives with the moving base simulator and can be used for work in which the impression of motion plays a less important role, such as validation of driver assist systems, HMI (human machine interface), and acoustics optimization.
The increased use of simulation—and particularly the positioning of systems on one site—means that at least one prototype stage is no longer required by Mercedes, thus saving time and hardware costs.
Dragon believes that the location of the simulators together with other R&D and design facilities in one center is unique in the automotive world: “The intensive sharing of knowledge between the individual areas contributes a lot to our ability to shorten development times while still significantly boosting the maturity of our products.”
One of the interesting areas for which simulators are being used is to enhance pedestrian safety, particularly at night. IR images via a head-up display represent one established solution, but Mercedes is considering using the car’s lighting system to briefly, specifically illuminate pedestrians in certain low light conditions.