## 1 Introduction  
The NVH problem of a vehicle has a significant impact on its comfort, with powertrain-generated vibrations being a key factor affecting NVH performance [1]. The suspension serves as an elastic system that connects the powertrain and the frame of an automobile. A suspension with excellent vibration isolation performance plays a crucial role in the overall NVH performance of a vehicle [2]. The reasonable static stiffness of the suspension can effectively reduce powertrain-generated vibrations, making it essential to deeply investigate the static stiffness of vehicle suspensions. [PERSON] [3] et al. developed a quasi-zero-stiffness suspension system that combines air spring and magnetic spring in parallel. They conducted mathematical modeling of the air spring and magnetic spring and tested the performance of the proposed suspension. The research revealed that the new suspension has a significant impact on reducing the acceleration of the vehicle body, provides effective vibration isolation for low-frequency vibrations, and lowers the natural frequency of the system. [PERSON] [4] established a suspension system model based on a CDC shock absorber. The analysis focused on the influence of suspension damping coefficient and suspension stiffness on the vibration characteristics of the suspension system from both time domain and frequency domain perspectives. It was found that suspension damping coefficient and stiffness are the key factors affecting the vibration characteristics of the suspension. [PERSON] [5] established a finite element model for the lateral leaf spring suspension. The study focused on analyzing the characteristics of stiffness, deformation, and stress change with distance in the lateral leaf spring suspension. This research provides a theoretical basis and reference for the design of lateral leaf spring suspensions. [PERSON] [6] proposed the optimal negative stiffness structure for the earth roller and suggested using hydraulic suspension to replace the traditional driver seat suspension system and the traditional rubber suspension in the cab. This provides an important reference for applying the optimal negative stiffness structure in other vehicle seat suspension systems, ultimately improving the driver's ride quality. [PERSON] [7] proposed an automotive test framework to assess the reliability and stability of advanced driver assistance systems. The study utilized a non-dominated ordering genetic algorithm (NSGA-II) to optimize the damping, stiffness, and installation position of the suspension system. The research revealed that the designed suspension performance showed significant improvement compared to previous studies. [PERSON] [8] developed a magnetorheological fluid controllable multi-channel suspension with adjustable dynamic stiffness and damping. The study found that the application of magnetic fields to different flow channels could minimize the dynamic stiffness and transfer rate of damping harmonic force in the suspension. This research contributes to the understanding of how magnetic fields can be used to optimize the performance of multi-channel suspensions. [PERSON] [9] designed a magnetorheological fluid suspension with multiple inertial channels and conducted a simulation study on the dynamic characteristics of the suspension. The findings indicate that the multi-inertial channel Magnetorheological fluid suspension can enhance the vibration isolation performance of the engine at idle speed. [PERSON] [10] designed a magnetorheological liquid-based engine mounting device and conducted a dynamic analysis of it. They established a dynamic decoupling calculation model of the magnetorheological mounting system and further optimized its structural parameters. [PERSON] [11] proposed a new mixed-mode magnetorheological hydraulic suspension.