Optimization of Dynamic Seating Comfort: Optimal Interaction Between Frequency Ranges, Resonance, and Isolation

To prevent disturbances to passengers caused by vibrations as early as the virtual development phase, it is crucial to optimize the interaction between the seat and the vehicle in terms of vibration transmission and resonance at an early stage. CASIMIR/Automotive offers the ability to evaluate the seat itself through the seat transfer function and simultaneously optimize the interaction of the seat and human with the vehicle by integrating it into the vehicle's multibody simulation.

Frequency ranges and their impact on comfort

When considering dynamic seating comfort, it is essential to define the relevant frequency range depending on the driving situation.

For typical ride comfort, that is, the interaction between the chassis, body, and seat, the frequency range up to the first vertical resonance of the human on the seat is generally significant, typically between 3 and 5 Hz.

In contrast, the vibration comfort of the seat typically starts at around 6 Hz and extends up to about 30 Hz. Vibrations at higher frequencies are only weakly transmitted by the seat to the human and are difficult to perceive due to their small displacement amplitude.

The goal of any dynamic seat optimization is to find the optimal compromise between minimal resonance amplification and effective isolation at higher frequencies, with the weighting varying depending on the vehicle type and manufacturer.

Prerequisite

For a valid simulation of dynamic seating comfort, the FE model of the seat structure must be dynamically validated through a modal analysis. Such models are often already available from NVH analyses. Additionally, the material properties of the foams must be supplemented with dynamic material parameters. The CASIMIR Material Manager supports this by taking over the material identification and creating the complete material card.

Assessment

The assessment of vibration comfort typically takes place using the seat transfer function. With CASIMIR/Automotive, this function can be directly determined. The goal is to achieve an optimal compromise between resonance amplification and effective isolation without local resonances occurring within the seat structure.

Ride Comfort analysis in driving situations

To analyse ride comfort, the interaction between the human, seat, and vehicle in various driving situations is examined. For this purpose, the human model is integrated as a flexible body into a multibody simulation (MBS) model of the vehicle (e.g., Adams / Simpack). This integration enables a realistic interaction between the vehicle, seat, and human, which significantly differs from the typical coupling of individual masses. Additionally, measurement points on the human model can be evaluated.