The riding comfort improvement by the paralleled semi-active magnetorheological damper and passive inertance suspension from the power perspective

Abstract

Extensive research demonstrates that a semi-active damper in combination with inerter-based suspension could improve the ride comfort and road-holding performance of vehicles. However, the inherent dynamics of a semi-active damper is always neglected. The underlying mechanism of the controller with inerter in different frequency ranges is not well understood. Accordingly, this paper investigated the quarter-car suspension consisting of the paralleled nonlinear hysteretic semi-active magnetorheological (MR) damper and a passive inerter. To study the influence of different strategies, the clipped optimum controlled- (COC) and the mixed skyhook power-driven damper (SKYPDD) controlled- MR damper with the inerter are both adopted and denoted as COCI and SKYPDI, respectively. The optimal inertance is selected to minimize the sprung acceleration. Since there lacks quantitative method to analyze the working mechanism of semi-active controllers, an innovative power-based criterion was proposed in this paper. The trajectory of the control force and the sprung mass velocity determines the equivalent damping ratio added to the sprung mass and the input power it receives from the unsprung mass. The sprung mass vibration is reduced by decreasing the input power or increasing the damping ratio. Under harmonic excitation, the additional inertance decreases the power input to the sprung mass in the low-frequency range and isolates the sprung mass from the forced vibration at the unsprung resonance. Under the broadband stochastic excitation, SKYPDI and COCI can effectively decrease the input power spectrum and increase the damping ratio spectrum in the dominant sprung mass resonance. A parametric study on varying stiffness ratio demonstrates the semi-active strategy takes effects mainly in the high-stiffness-ratio range where the additional inertance more evidently enhances the damping ratio, especially for COCI. In summary, this paper proposes the power-based criterion for analyzing the working mechanism of semi-active strategies in ride comfort improvement.