Performance analysis of MISD suspension with conical pendulum displacement-dependent mem-inerter

This study investigates the equivalence relationship between mem-inerters and semi-active inerters while assessing the performance of suspension systems with mechanical conical pendulum mem-inerters. Two mem-inerters with displacement-dependent relationships (positive and negative correlation) are developed, enabling the suspension system to autonomously adapt to varying loads without relying on sensors, controllers, or external power. The memory characteristics of the mem-inerters are confirmed through algebraic analyses and pinched hysteresis loops. To further investigate the suspension performance with the displacement-dependent mem-inerter, the MISD (Mem-Inerter-Spring-Damper) suspension model is established. According to the equivalent inertance theorem, the proposed mem-inerters can replicate the behavior of semi-active inertance control strategies. Subsequently, we demonstrated the functional equivalence between semi-active inerters and mem-inerters with inertance-displacement relationships through frequency-domain characteristic analyses. Numerical simulation tests compared the performance of the MISD against conventional passive system. Simulation results show that the positive correlation mem-inerter reduces body acceleration RMS values by 10.02% (no load), 11.55% (quarter load), 13.29% (half load), and 15.84% (full load) compared to the passive suspensions. These reductions consistently surpass those of the negative correlation mem-inerter. Furthermore, HiL (Hardware-in-the-Loop) test was conducted to analyze equivalent semi-active suspension performance. The effectiveness of the MISD suspension in vibration mitigation is verified by the fact that the suspension with the equivalent semi-active inerter has a smoother and higher ride quality than the passive one. This study improves passive suspension performance through direct substitution of linear inerters with conical pendulum mem-inerters, offering a passive yet adaptive suspension solution for practical automotive applications.