2.1 Introduction
Scalable dummy models and human models can be used for the design of safer vehicles and
restraint systems. With such dummy models the safety of vehicles can be evaluated for subjects
with an anthropometry that is different from the available dummies. This is relevant for
instance for the design of .smart restraint systems.. For accident reconstructions it is considered
important to have a model that describes the anthropometry of the victim with sufficient
accuracy. In general, the size and weight of accident victims deviates considerably from any
available dummy. Sometimes models with an extreme anthropometry are required.
A method has been developed to generate models of subjects with varying anthropometry.
This method has been applied to crash-dummy models and human body models. The method
requires a parametrized description of the anthropometry of a dummy model, the reference
dummy model. This model is scaled to a model with the same structure (bodies, ellipsoids,
force models) as the reference model, but with the specified anthropometry. The first step of
the method is to generate a set of key parameters from a relevant population that describes the
anthropometry of the target occupant, The anthropometries of the reference dummy models
that are available for scaling, have also been described with this set of parameters. The second
step is to scale the reference model towards the desired anthropometry. Different scaling
factors are applied for the different body parts and dimensions. These factors are used to derive:
body dimensions, mass and inertia properties, joint locations, ellipsoid dimensions, force
models, joint models and contact characteristics.
A graphical impression of scaled Hybrid-III dummy models using this approach is given in
Figure 2.1.
2.2 Considerations for use
Some limitations apply to the MADYMO scaler that are important to keep in mind when
performing a scaling operation:
? The database that is used to scale the dummy model represents humans, not dummies.
A 50th human male does not have the same dimensions and weight as a Hybrid-III 50th
percentile dummy - the latter is smaller in size (when placed in a standing position). The
same applies to the 5th female dummy model. This means that when percentiles are
used, the scaled dummy models will not correspond to dummy percentile values. Scaling
a 50th percentile Hybrid-III dummy using 50th percentile human body dimension
values will result in a larger dummy model
? The body segment proportions of humans and dummies are not the same. This means
that individual dimensions of body segments may change by the scaling process, even if
the overall dimensions are not affected by the scaling process. For example, the human
body data suggests larger arm and leg dimensions. A scaled dummy model will therefore
have longer arms and lengths when compared to the overall body length than the
unscaled model. If the body segment proportions must be maintained, the user should
use the .fixed scale factors. method to scale the dummy (see Section 2.4.4 for details).
? The MADYMO/Scaler does not translate the parameterized files of a previous MADYMO
release to the current release.
2.3 Usage of MADYMO/Scaler
MADYMO/Scaler requires a special input file with the extension ’.dat.’. This file is described
in Sec. 2.4. It defines the dummy model that has to be scaled (the reference dummy model)
and the desired anthropometry. The scaling process is illustrated in Fig. 2.2.
To start MADYMO/Scaler type:
madymo74 -madyscal filename[.dat]
The following reference dummy models are available for scaling:
d_hyb36yel.par Sitting 6 year old Hybrid III
d_hyb305el.par Sitting 5th percentile female Hybrid III
d_hyb350el.par Sitting 50th percentile male Hybrid III
d_hyb350faael.par Sitting Hybrid III 50th percentile male FAA
d_shb350el.par Standing 50th percentile male Hybrid III
The desired anthropometry can be specified in a simple way using MADYMO/Dummy Generator.
This requires only the mass and/or body standing height (and/or age for children).
The relevant routines from MADYMO/Dummy Generator have been integrated into the MADYMO/
Scaler program, and these are used to generate a set of 35 anthropometric parameters (see Table 2.1). For a detailed description of the anthropometric parameters, the user is referred
to Section 3.2 Alternatively the user may directly define these 35 parameters. This set of parameters
may be generated withMADYMO/Dummy Generator and then edited to describe a
specific subject. These parameters may also be derived from other anthropometry sources like
RAMSIS. This approach was used in a study performed by Happee et al. (1998).
A subset of the 35 parameters in Table 2.1 is used for scaling. For every reference model the
corresponding parameters have also been evaluated. In the first part of the scaling, scaling
factors are simply obtained as the ratio of the previously mentioned subset of parameters for
the desired and the reference model. Thus various scaling factors are derived for separate
body parts and for x, y and z directions. The resulting scaling factors are then applied to the
reference model. The default scaling factor for standing height is applied for the parameters
in Table 2.1 that are set to 0.0. The value 0.0 is not allowed for parameters 2, 6 and 24.
The scaling process uses non-linear methods developed at TNO Automotive. These methods
enable scaling of all mechanical parameters, including joint stiffness and damping. Background
information on the scaling method is given later in this section.
After the first part of the scaling, the mass and the main dimensions of the resulting model are
checked. The totalmass of the scaledmodel is only an indirect result of the scaling process and
therefore normally deviates slightly from the specified mass. The main dimensions (standing
height, seated height and shoulder breadth) may deviate slightly from the target values due
to various factors complicating the scaling.
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