Fluid Inerter Based Vibration Suppression: Modelling Methodology

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


Inerter is the mechanical analogue of the capacitor via the force-current analogy. It has the property that the force across the terminals is proportional to their relative acceleration. Vibration absorbers with a combination of stiffness, damping and inertance have been shown to be effective through numerous theoretical studies.
A case study is carries out to investigate the potential reduction in road damage by incor- porating the inerter element into truck suspension systems. Initially, quarter-car, pitch-plane and roll-plane models with two low-complexity inerter-based linear suspension layouts are inves- tigated in the frequency domain. Reductions of the J95 road damage index for each model are identified against conventional parallel spring-damper truck suspension layouts. Subsequently, the nonlinearities of leaf springs are incorporated into the pitch-plane and roll-plane time-domain models. It has been verified that the benefits brought by the inerter integrated suspension are still present.
There are mainly two types of physical realisation for the inerter. Compared with flywheel- based inerters, the fluid-based forms have advantages of improved durability, structural simplicity, inherent damping and similarity with existing damper constructions. In this work, two prototypes of a helical-tube fluid inerter and a fluid-inerter integrated damping (FID) device are built for the modelling studies.
In order to improve the understanding of the physical behaviour of the fluid-based devices, especially caused by the hydraulic resistance and inertial effects in the external tube, this work proposes a comprehensive model identification methodology. Firstly, a modelling procedure is established, which allows the topological arrangement of the mechanical networks to be obtained by mapping the damping, inertance and stiffness effects directly to their respective hydraulic counterparts. Secondly, an experimental sequence is introduced, which separates the element- property identifications into smaller subsets. Meanwhile, an experimental set-up is introduced, where two pressure gauges are used to accurately measure the pressure drop across the external tube. Using the proposed modelling methodology, the theoretical models with improved confidence are obtained for a helical-tube fluid inerter prototype.
Furthermore, previous studies focused on accurate modelling of a specific fluid-based inerter device, while there has been no investigation on whether the dynamic models are still valid when its design parameters change. A model is termed here as being generalisable when it is able to sufficiently accurately characterise the terminal behaviour while allowing its design parameters to vary within their pre-defined ranges. Therefore, the generalisable model is developed for an example FID device design. The sources of remaining discrepancies are further analysed. The methodology to establish the generalisable model presented here is applicable to other design parameter selections as well as other designs of fluid-based vibration suppression devices.
Date of Award25 Jun 2019
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorJason Zheng Jiang (Supervisor) & Branislav Titurus (Supervisor)

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