Frequency-dependent equivalent impedance analysis for optimizing vehicle inertial suspensions

This work proposes a frequency-dependent equivalent impedance (FDEI) method for analyzing the dynamic behavior of mechanical networks and enhancing vehicle inertial suspension performance through structural optimization. We investigate the equivalent impedance of two-element and three-element mechanical networks, leveraging these characteristics for both inerter design and suspension applications. The study explains the relationships between equivalent stiffness, equivalent damping, and equivalent inertance with their associated parameters. A suspension model is analyzed to explore the fundamental relationship between equivalent impedance and suspension performance. Additionally, a nonlinear dynamic model of the fluid inerter is established and analyzed using FDEI. The fluid inerter prototype is fabricated and tested with parameters identified and output force verified through bench tests. Experimental results indicate that nonlinear factors have varying effectiveness across different frequency ranges. An inertial suspension model incorporating a nonlinear fluid inerter is also established. The performance of traditional suspension, inertial suspension with an ideal inerter, and inertial suspension with a nonlinear fluid inerter is compared. Results show that the designed inertial suspension structure can significantly improve vibration isolation quality, despite nonlinear factors somewhat compromise performance. The FDEI analysis method is proposed to improve vehicle inertial suspensions and present guidelines for the design of inerter-based vibration isolators.