A range of real-world road surfaces was turned into a data stream that enabled Ford to optimize the mass damping of the seats in the new 2009 Flex crossover. The approach, to counter effects of road irregularities in the computer-aided engineering stage, was explained by a team of Ford engineers at April’s SAE 2008 World Congress.
The computer simulation of the road surfaces meant that mass damping could be optimized before the prototype stage, so all that remains is fine-tuning, explained Qin Pan, the project leader.
The new approach also will be used in other Ford vehicles, from the new F-150 to the Focus. However, it does not mean that all seats will be virtually the same under the cover materials.
“We set up a comfort DNA range that spans small cars through trucks,” said Jerry Brown, Chief Engineer, North American Seat Engineering, referring to “F-Family” seats, a new Ford seat architecture. So, Mustang seats get more road input because the buyers want that, but other buyers who want more isolation get that, he said.
It is important that the seat’s natural frequencies be separated from the full vehicle system's resonant frequencies to avoid seat vibration, according to Pan and fellow engineers Joanna Rakowska, Mike Medoro, and Swami Perumalswami. Their paper describes a method to design a mass damper that not only separates the seat modes from the vehicle's specific resonant frequency range, but also reduces the seatback vibration amplitude significantly.
The response surface based optimization has turned out to be successful in tuning the damper parameters to reduce seat vibrations, the engineers say. The method is more efficient and reliable than the traditional trial-and-error method. Once the response surfaces are generated, multiple optimization runs can be easily performed with different constraints for frequencies and amplitudes for both longitudinal and lateral modes. This allows for minimizing the damper mass while achieving the best placement of the frequencies and the peak amplitude reduction to minimize the interaction with the vehicle modes.