## 4 Research on Dynamic Seat Comfort
### Experimental Validation of the Dynamic Model  
To further investigate the vibration transmission characteristics of the seat suspension and validate the accuracy of the developed dynamic model, an experimental system of seat vibration transmission characteristics was constructed utilizing an MTS hydraulic servo system. The test photo of the transmission characteristics of the seat is shown in Figure 12. The vibration test platform is controlled via a hydraulic servo system, enabling the generation of sinusoidal sweep vibrations with variable amplitude and constant intensity. The frequency range of the vibration spans from 0.5 Hz to 30 Hz, which encompasses the critical frequency band to which the human body exhibits heightened sensitivity in terms of vibrational perception. The seat dynamic comfort tests were performed in accordance with ISO 17025 [14] requirements, with laboratory temperature maintained at 20-25 \({}^{\circ}\)C and air relative humidity controlled at 40-60%. The experimental protocol employed sinusoidal sweep excitation signals within the frequency range of 0.5-20 Hz, and the platform acceleration was maintained at a root mean square RMS value of 2 m/s\({}^{2}\). An air compressor was used to change the air pressure in the air spring to make the seat reach different heights. The seat was fixed at the center position of the excitation table, a weight was placed at the middle position of the cushion, and two acceleration sensors were used to measure the response of the excitation table and the vibration response on the surface of the cushion [15]. A total of nine operating conditions were tested in this study. For each condition, three independent trials were conducted, and the results were averaged to obtain the final experimental data for that condition. To ensure result consistency, all three trials for each operating condition showed less than 5% variation in key metrics. The data were input to a PC through an acquisition system, and the vibration transmission characteristic curve of the seat was obtained after processing. By applying the excitation signal to the system and processing and analyzing the data collected by the acceleration sensor, the vibration transmission characteristics of the seat were obtained. In the experiment, three levels of damping values and three levels of seat heights were set to  
Figure 12: The experimental system. carry out crossover experiments (e.g., RMS acceleration, vibration transmissibility). This repeatability demonstrates the reliability of the experimental data. Dynamic simulations were carried out according to the above experimental conditions, and the experimental and simulation results were compared, as shown in Table 2.  
From the overall analysis above, it can be seen that the error between the seat dynamic comfort experiment and the simulation is controlled within 15%, which proves that the established dynamic model is highly reliable. The sources of the error between the experimental and simulation data were analyzed, and the reasons for the median error may be as follows:  
(1) During the dynamic modeling of the seat, the secondary structures of the seat were overlooked, and these components may contribute to vibration transmission in the experiment. (2) The super elastic or viscoelastic behavior of the seat foam material was simplified as a linear model in the simulation, resulting in errors between the damping characteristics and the experiment. (3) In the simulation, it is assumed that the components have an ideal contact with fixed constraints or a constant coefficient of friction, but in reality, there exist complex contact behaviors such as minor slippage and gap changes. (4) Boundary condition deviation: the installation stiffness of the seat and the vibration table in the experiment was inconsistent with the ideal fixed constraint in the simulation, which affected the natural frequency of the system.