Modelling and design of a novel air-spring for a suspension seat
Date
2008-03
Authors
Holtz, Marco Wilfried
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
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.
Description
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008.
Keywords
Dissertations -- Mechanical engineering, Theses -- Mechanical engineering, Suspension seats, Vehicles -- Vibration, Vibration damping, Trucks -- Springs and suspension