11 research outputs found
Car seat and occupant modelling using CAD
A current Brite-Euram project is concerned with life-cycle aspects of car seating with Loughborough being responsible for driver comfort assessment. This is being carried out through road and laboratory trials, with the results to be incorporated within the SAMMIE design system. Driver comfort is in part determined by seat pressure distributions which lead to deformation of the human flesh and the seat and movement of important design locations such as the driver's eyepoint. Accommodation of these effects requires a more realistic representation of the human body using surface rather than solid representations. Hence a shadow scanning technique is used to capture human body shape which is processed into the DUCT surface modelling system and via IGES files into SAMMIE. Finite element techniques are then used to predict deformations at the seat/driver interface
Biomechanical model of the human spine as an arch
Biomechanical model of the human spine as an arc
Spine modelling and "safe to use" equipment design
Computer human modelling has for sometime been developed and used but even the most sophisticated commercially available human modelling packages do not have an effective spine model. Although some packages have a geometric representation of the spine, they have no analytic or design application functionality. On the other hand back pain and back injuries are well-known to be a major problem and lead to substantial costs to manufacturing industry through enforced absenteeism. The main objective is to provide an answer to the need for a design tool which can consider the range of postures and predict the loads that will be imposed on the spine
Internal forces in the spine modelled as an arch
The work reported here presents a parametric solid model of the spine, loading systems
of the spine and a extracted arch spine model in which the body weight and external
loads are treated as forces applied at appropriate points on the spine and muscle and
ligament forces are treated as reaction forces applied to both ends of the spine. The
model extends the arch spine approach by using optimisation techniques to find a better
fitting thrust line compared with the previous arch model in the literature, and calculates
the internal forces between the vertebrae in the spine. Case studies show the reasonable
values of the internal forces (1.1-1.5 kN) in the arch spine. The values are much less than
that of lever models (up to 6.6 kN)
Computer aided modelling of the human spine
The human spine is the main structure to support human body weight and external loads,
to allow the torso to reach to a variety of positions and to protect the spinal nervous system.
Lumbar back pain and disorders may be related to spinal curvature and disc pressure, and it is an
ultimate objective of the work reported here to include consideration of these issues in computer
aided ergonomics design systems for evaluating a wide range of situations including manual
handling and car seat design.
Several methods from structural analysis have previously been used to model the human spine,
principally lever and beam structures, but these have frequently shown discrepancies when compared
with experimental data. As an alternative, an arch representation for the spine is considered here
and allows the establishment of a criterion for the failure of the spine that may be useful in
determining absolute maximum loading conditions. However, the main interest is in submaximal
loading conditions where damage or discomfort are the concerns rather than fracture. It is proposed
that the location of the thrust line in relation to the centre-line of the spine is a useful predictor, and
optimization techniques have been developed to find the ‘best-fitting’ thrust line for the statically
indeterminate structure.
Further work is concerned with adding muscle and ligament forces to the loading system of the
model, extension of the two-dimensional model into three dimensions, validation against experimental
data and integration with the SAMMIE computer aided ergonomics design system
Mathematical modelling of human spine and design
Many individuals suffer from back trouble and a large number of sufferers provide a
hidden cost to industry, from the increasingly high level of absenteeism. Back pain and injury
may result from inadequately designed artefacts and workplaces. In order to achieve better
designs which prevent such injuries one has to have a greater understanding of the source of
the problems. The mechanics of human spine can be studied by conducting experiments
directly on humans in a laboratory. Alternatively mathematical models which represent
subtleties and geometric complexities may be studied. Such models of human spine could look
at how the spine behaves in specific situations. This paper is about generating a general
purpose spine model that is suited a wide range of design applications. The geometric model
and the mathematical modelling aspects will be explained. The result of the research
infeasibility of range of models representing the spine will also be discussed. The paper will
conclude with suggestions on the potential use of human spine models in design
Stability of the spine modelled as an arch
The erector muscles are frequently strained through improper lifting. Stability of the
spine is maintained by the muscles, ligaments and pressures inside the body cavities. Modelling
of this stability has been achieved using a new arch spine model developed using optimisation
techniques. The position of the thrust line in the arch spine model can be used to analyse
stability of the spine, and muscle forces introduced to change the position of this thrust line.
The erector muscles move the thrust line forward to the centre line of the spine in a weight
lifting task in a stooped posture. A method to calculate muscle forces stabilising the spine and
to calculate internal forces in the vertebrae is presented. Calculations show that L3/L4 disc
loads increase with muscle and ligament forces in the lumbar region
Modelling the human body for ergonomic CAD
A recently completed Brite-Euram (European Community) research project was concerned
with life-cycle aspects of car seating with Loughborough University being responsible for driver
comfort assessment. This was achieved by road and laboratory trials, with the results to be
incorporated within the SAMMIE computer-aided ergonomic design system. Driver comfort is in part
determined by seat pressure distributions which lead to deformation of the human flesh and the seat
and result in uncertainty in the position of important design locations such as the driver's eyepoint.
Accommodation of these effects requires a realistic representation of the human body using surface
rather than solid representations. Hence a shadow scanning technique was used to capture human
body shape which was processed into the DUCT surface modelling system and via IGES files into
SAMMIE. Finite element techniques were then used to predict deformations at the seat/driver
interface. Having established an anthropometrically correct representation of body shape, current
research is aimed at improving the kinematic and analytic capabilities of the human model by
introducing a multi-segment spine that can respond to external and internal loadings. This spine
model is intended for use in the evaluation of human working postures (such as car driving) where,
although the loadings might be viewed as well within human capabilities, previous studies have·
shown that back pain or damage might result. The model described is based on an arch representation
rather than the pin-jointed rigid link systems which are perhaps more usual, but which have been
shown to be deficient in several respects
Computer aided modelling of the human spine
The human spine is the main structure to support human body weight and external loads, to
allow the torso to reach to a variety of positions and to protect the spinal nervous system.
Lumbar back pain and disorders may be related to spinal curvature and disc pressure, and it is
an ultimate objective of the work reported here to include consideration of these issues in
computer aided ergonomics design systems for evaluating a wide range of situations including
manual handling and car seat design.
Several methods from structural analysis have previously been used to model the human
spine, principally lever and beam structures, but these have frequently shown discrepancies
when compared with experimental data. As an alternative, an arch representation for the spine
is considered here and allows the establishment of a criterion for the failure of the spine that
may be useful in determining absolute maximum loading conditions. However, the main
interest is in sub-maximal loading conditions where damage or discomfort are the concerns
rather than fracture. It is proposed that the location of the thrust line in relation to the centre
line of the spine is a useful predictor, and optimisation techniques have been developed to
find the 'best-fitting' thrust line for the statically indeterminate structure.
Further work is concerned with adding muscle and ligament forces to the loading system
of the model, extension of the 2D model into 3D, validation against experimental data and
integration with the SAMMIE computer aided ergonomics design system
Computer aided analysis of deformation and pressure distribution at the driver/seat interface
Analysis of deformation and pressure distribution at the driver/seat interface is valuable for
ergonomic analysis and improving the comfort of car seat designs. This paper presents human
body surface modelling using a shadow scanning technique, car seat modelling and nonlinear
finite element analysis of deformation and pressure distribution at the driver/seat
interface. In order to avoid the difficulties in the calculation of direct 3D force loading a
technique of determining reaction forces from the displacement between the human body and
the car seat was used. The results of deformation and pressure distributions at the driver/seat
interface are presented which were found to be qualitatively comparable with experimentally
derived measurements although peak pressures were 2-4 times greater. The reasons for this
difference are presented