Thesis-2009-Jaiswal.pdf (43.08 MB)
Download fileThe interaction of tyre and anti-lock braking in vehicle transient dynamics
thesis
posted on 2014-07-14, 10:45 authored by Manish JaiswalThe thesis presents an intermediate modelling approach to study transient behaviour of vehicle
systems, with emphasis put on simplified yet accurate representation of important system
elements. A representative non-linear vehicle model is developed in MA TLAB/Simulink
environment, where non-linear characteristics of tyre, suspension and braking system are
included to capture the dynamic behaviour of a vehicle under transient conditions. The novel
aspect of this work is the application of a representative full vehicle-tyre-ABS integrated set-up
to study the complicated interaction between tyre and anti-lock braking, under a range of
demanding operating conditions, including combined cornering and braking ..
The modelling methodology involves development of low end vehicle models, based on the
Newton-Euler formulation. Subsequently, an intermediate vehicle model is devised, where more
details are incorporated such as additional DOF to capture the sprung mass motion in space,
along with its non-linear interactions with the un-sprung masses, large angle effects, kinematics
of steering/wheels and an appropriate tyre model suitable for transient manoeuvres. Particular
attention is paid to the suspension system modelling, through inclusion of non-linear effects in
springs, dampers, bump-stops, and anti-roll bars, along with the jacking and anti-dive effects
using the virtual work method. The model also incorporates a hydraulic brake model, based on
the reduced order brake system dynamics for realistic simulation of the braking manoeuvres.
A complex multi-body ADAMS/Chassis model, with much greater level of detail, has also been
established to extensively compare and enhance the realistic behaviour of the intermediate
vehicle model. During the simulation exercise, the intermediate vehicle model has shown good
agreement with the complex ADAMS model, thus justifying the accurate representation of
vehicle.non-linear characteristics, particularly the suspension system. The realistic behaviour of
the vehicle model is further ascertained with a reliable GPS enabled test vehicle, by performing
number of manoeuvres on test tracks, including combined cornering and braking.
A representative 4-channel conventional ABS system is modelled and integrated in the
intermediate vehicle model. The ABS adopts generic peak seeking approach, employing wheel
deceleration and brake slip as control variables. External braking inputs, in form of stepped
pressure pulses, are also separately used to represent the transient braking system dynamics.
In the current work, different transient tyre models based on the single point contact approach
and using Magic Formula steady-state characteristics are applied, while studying the influence of
their dynamic behaviour on the ABS system. By employing a representative ABS system in a
multi-body vehicle model and considering the particularly demanding situation of combined
braking I cornering, it is shown that the models which are adequate for pure braking might
struggle when the complicated full vehicle dynamics are excited. It is shown that the first order
relaxation length approach may not be sufficient to fully satisfy the requirements of an ABS
braking, especially if the relaxation length is not modelled as a variable dependent on tyre slip.
In comparison, the modelling approach, where the carcass compliances and contact patch
properties are explicitly represented, can handle the oscillatory tyre behaviour associated with
ABS braking, in a far more accurate manner. In comparison to the earlier studies, which were
mostly conducted for straight-line braking, this thesis stresses the fact that the tyre behaviour can
be influenced by the complex interaction of handling and braking, and hence the effect should be
captured while investigating or evaluating the performance of a tyre model in relation with ABS
simulation.
History
School
- Mechanical, Electrical and Manufacturing Engineering
Publisher
© Manish JaiswalPublication date
2009Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Language
- en