Nonlinear dynamic properties of hydraulic suspension bushing with emphasis on the flow passage characteristics

Abstract

Hydraulic bushings, which are often employed in vehicle suspension systems, exhibit significant excitation-dependent properties. However, previous analyses were mainly based on the linear system theory. To overcome this void, nonlinear characteristics of common hydraulic bushing configurations are examined in this article, with focus on the component properties as excited by sinusoidal or step displacements of various amplitudes. First, a nonlinear model for a laboratory prototype with a long passage and a short passage (in parallel) is developed using a lumped-parameter approach. Then the system parameters and nonlinearities are identified using experimental and computational methods, with an emphasis on characterization of the flow passage resistances. Steady-state harmonic and transient step experiments are conducted on the prototype, and the dynamic pressures inside two fluid chambers and the force transmitted to the base are measured. Numerical solution of the nonlinear model shows that the proposed model predicts both steady-state sinusoidal responses and transient responses well for single-passage and dual-passage configurations; significant improvement over a corresponding linear model is observed. Finally, approximate analytical and semi-analytical solutions of the nonlinear model are obtained by using the harmonic balance method.

Harmonic amplitude dependent dynamic stiffness of hydraulic bushings: Alternate nonlinear models and experimental validation

“…Hydraulic elastomeric devices are often employed in automotive powertrain and suspension systems because of their unique dynamic properties, leading to both vibration isolation and motion control [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. These properties are achieved by an internal fluid system working in tandem with the elastomeric structure of a bushing.…”

“…These properties are achieved by an internal fluid system working in tandem with the elastomeric structure of a bushing. Despite some similarities with hydraulic engine mounts that have been extensively studied [1][2][3][4][5][6][7][8][9], the behavior of hydraulic bushings is quite different and merits its own in-depth studies [10][11][12][13][14][15][16][17][18]. Prior, though limited, investigations of these devices have largely focused on simpler transfer function type formulations based on the linear time-invariant (LTI) system theory [10][11][12][13][14][15][16].…”

“…For instance, Arzanpour and Golnaraghi [12] developed a reduced order linear system model for a hydraulic bushing which attempts to capture some aspects of the physics, such as fluid resistance, compliance, and inertance. Chai et al [13][14][15][16] further developed the linear models for frequency and time domain characteristics for a laboratory bushing device and even introduced a nonlinear fluid resistance term [17]. Fredette et al [18] recently developed a new laboratory experiment to measure the nonlinear fluid compliance of hydraulic bushing pumping chambers.…”

“…Under harmonic excitation, hydraulic bushings exhibit significant amplitude dependent behavior [10,11,[14][15][16][17][18], which cannot be described by the linear time-invariant system theory.…”

“…The chief goal of this article is therefore to propose new or improved quasi-linear and nonlinear reduced-order hydraulic bushing models, predict amplitude sensitivity characterization under harmonic loading, and experimentally validate alternate nonlinear models. Additionally, the prior work [17] on the multi-term harmonic balance method will be extended and refined to explain the underlying physics.…”