Comparative Vibration Isolation Assessment of Two Seat Suspension Models with Different Negative Stiffness Structure

This study proposes two isolation models of the negative stiffness structure (NSS) using the air spring (NSS-AS) and the tuned mass damper (NSS-4) to improve the ride comfort of electric vehicles (EV). The dynamic models of the EV and the driver body are established under the vibration excitations of the in-wheel motor (IWM) and random road surface. Based on the root-mean-square acceleration of the driver’s head (a w1), the seat suspension models equipped with the NSS-AS and NSS-4 are simulated to evaluate their isolation performance in improving the EV ride comfort under various conditions. The research results show that when the EV is moving on the road surface of ISO level A at a speed of 20 m/s, both NSS-AS and NSS-4 added into the seat suspension can better improve the driver’s ride comfort in comparison to that without NSS. Especially, the a w1 with the NSS-AS is decreased by 18.7% in comparison with the NSS-4. In addition, at the high-speed region over 22.5 m/s of the EV moving on the different road surfaces of ISO levels A, B, and C, the a w1 with the NSS-4 is quickly increased and higher than that of the NSS-AS, while the a w1 with the NSS-AS is slowly increased. Moreover, under the effect of the eccentricity of the rotor and total mass of the motor rotor and tire, the a w1 with the NSS-AS is also lower than that of the NSS-4. Therefore, the driver’s ride comfort and the isolation performance of the seat suspension using the NSS-AS are better than that of the NSS-4. This means that the NSS-AS should be applied to the EV seat suspension to better improve ride comfort.