Development of inerter-based suspension systems for railway vehicles

  • Tim D Lewis

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


The suppression of unwanted railway vehicle vibrations and the reduction of
maintenance costs associated with tracks and wheels are two vitally important objectives for the railway industry. The trade-off between passenger comfort and trackwear, which has long plagued railway vehicle dynamicists, arises from the Primary Yaw Stiffness’s propensity to inhibit the wheelsets to yaw, increasing slip and hence increasing forces at the wheel-rail contact patch, yet decreasing the acceleration of the carbody. Active railway vehicle control methods have successfully been implemented, to reduce the need for a high Primary Yaw Stiffness. However, with the introduction of the inerter, scope for passive control, which does not run the risk of measurement error or require power input to deliver similar benefits, has greatly expanded. This thesis studies the extent to
which the inerter can be of benefit to both the curving and straight running performance of railway vehicles, by way of the optimisation of inertance-integrated passive suspension layouts. A variety of modelling approaches are employed, most notably numerical simulation and optimisation in MATLAB®, and more accurate, nonlinear analysis using the multi-body railway vehicle modelling software VAMPIRE®.

A two-axle railway vehicle model is considered in MATLAB®. Straight running
and curving performance is analysed by respectively subjecting the vehicle to a variety of straight, rough tracks, and a curve defined by ramped cant and curvature inputs. It is shown that the trade-off between passenger comfort and trackwear can be improved through the use of optimised, inertance-integrated lateral suspensions, with a further improvement discovered when an optimised HALL-Bush structure is used in the longitudinal direction. With the aim of validating the initial results, a location matrix technique of dynamic system simulation is developed which enables Laplace domain optimisations to take place on linearised VAMPIRE® models.

The final section of this thesis combines MATLAB® and VAMPIRE®, for respectively optimisation and multi-body dynamics modelling purposes. It demonstrates that the Primary Yaw Stiffness of a four-axle, industrial railway vehicle model can be significantly lowered, hence wheel and track maintenance costs decreased, whilst optimised inertance-integrated primary suspensions enable the ride quality to remain satisfactory. The structure-immittance approach to network-synthesis is used to identify beneficial suspension configurations, and numerous contact conditions and velocities are considered in the optimisation to cover a wide range of operating conditions. Further reality checks are performed on the vehicles with beneficial suspension configurations, the results of which reveal no significant detriment to other performance indices.

The findings of this project form an intermediate step towards the anticipated
adoption of inertance-integrated suspension systems by the railway industry. These devices, if tailored and incorporated correctly, have the potential to significantly reduce track and wheel maintenance costs, as well as improve stability for future generations of rolling stock.
Date of Award12 May 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorJason Zheng Jiang (Supervisor) & Simon A Neild (Supervisor)

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