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Design, development and testing of a 2-DOF articulated dump truck suspension seatBarnard, Charl 03 1900 (has links)
MScEng / This project entails the design and development of a new 2-DOF articulated dump
truck (ADT) suspension seat. A study of the ADT vibration environment was
conducted using data measured with accelerometers inside the cabin. With the
system’s required operational capabilities determined, the concept design phase
resulted in a feasible concept. The first prototype was manufactured based on the
initial set of specifications.
A variety of numerical modelling techniques were used to analyse and evaluate
the seat’s dynamic response. Vertical and lateral laboratory tests of the suspension
seat with human occupants were completed. The vertical lumped parameter model
of the suspension seat with a human occupant gave good correlation with the
laboratory measured frequency response.
A broad band input signal, and not the ISO 7096 (2000) EM1 signal, was used to
obtain the frequency response used to verify the lumped parameter model. The
SEAT values for the ISO 7096 (2000) EM1 signal and various ADT road
conditions were calculated using the lumped parameter models for a small,
medium and large subject, the same three subjects used in the laboratory tests.
SEAT values using the ISO 7096 (2000) EM1 signal of 0.94, 0.93 and 0.88 were
obtained for the small, medium and large subjects. The lowest SEAT values
obtained using the road data were 0.63, 0.56 and 0.48 for the small, medium and
large subjects. The transmissibility curves determined from the lateral laboratory
tests were used to calculate the SEAT values for the lateral ADT cabin vibrations.
The lowest SEAT values obtained were 0.83, 0.83 and 0.82 obtained for the small,
medium and large subjects.
After all the results from the testing and modelling were evaluated the design was
assessed. All the data and information collected was used as input for the design
of a second prototype, which was not manufactured. Not all the set specifications
were achieved for the first prototype, but the new suspension seat gave comparable vertical vibration isolation performance to that of expensive
commercially available ADT suspension seats. The lateral suspension
demonstrated good lateral vibration isolation and is a feature not currently
available in current ADT suspension seats.
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Suspension system optimisation to reduce whole body vibration exposure on an articulated dump truckKirstein, Johannes Cornelis 12 1900 (has links)
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2005. / In this document the reduced order simulation and optimisation of the passive suspension
systems of a locally produced forty ton articulated dump truck is discussed. The
linearization of the suspension parameters were validated using two and three dimensional
MATLAB models. A 24 degree-of-freedom, three dimensional ADAMS/VIEW model
with linear parameters was developed and compared to measured data as well as with
simulation results from a more complex 50 degree-of-freedom non-linear ADAMS/CAR
model. The ADAMS/VIEW model correlated in some aspects better with the experimental
data than an existing higher order ADAMS/CAR model and was used in the suspension
system optimisation study. The road profile over which the vehicle was to prove its
comfort was generated, from a spatial PSD (Power Spectral Density), to be representative
of a typical haul road. The weighted RMS (Root Mean Squared) and VDV (Vibration Dose
Value) values are used in the objective function for the optimisation study. The
optimisation was performed by four different algorithms and an improvement of 30% in
ride comfort for the worst axis was achieved on the haul road. The improvement was
realised by softening the struts and tires and hardening the cab mounts. The results were
verified by simulating the optimised truck on different road surfaces and comparing the
relative improvements with the original truck’s performance.
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Modelling and design of a novel air-spring for a suspension seatHoltz, Marco Wilfried 03 1900 (has links)
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008. / Suspension seats are commonly used for earth moving machinery to isolate
vehicle operators from vibrations transmitted to the vehicle body. To provide the
required stiffness and damping for these seats, air-springs are typically used in
conjunction with dampers. However, to eliminate the need for additional dampers,
air-springs can be used in conjunction with auxiliary air volumes to provide both
spring stiffness and damping. The damping is introduced through the flow
restriction connecting the two air volumes.
In this study, simplified models of an air-spring were derived followed by a model
including the addition of an auxiliary volume. Subsequent to simulations, tests
were performed on an experimental apparatus to validate the models.
The air-spring models were shown to predict the behaviour of the experimental
apparatus. The air-spring and auxiliary volume model followed the trend
predicted by literature but showed approximately 27 % lower transmissibility
amplitude and 21 % lower system natural frequency than obtained by tests when
using large flow restriction diameters. This inaccuracy was assumed to be
introduced by the simplified mass transfer equations defining the flow restriction
between air-spring and auxiliary volume. The models however showed correlation
when the auxiliary volume size was decreased by two thirds of the volume
actually used for the experiment.
This design of a prototype air-spring and auxiliary volume is presented for a
suspension seat used in articulated or rigid frame dump trucks. The goal of this
study was to design a suspension seat for this application and to obtain a SEAT
value below 1,1. The design was optimised by varying auxiliary volume size, flow
diameter and load. A SEAT value of less than 0,9 was achieved.
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