A sample AnyScript model
This is the beginning of our development of a model of the lower
extremity in AnyBody's modeling language, AnyScript. This simplified and
preliminary version of the model comprises the foot and the tibia
connected by the ankle joint. The model has only the soleus and the
tibialis anterior muscles.
Old followers of the AnyBody project will know how important a progress
this simple model symbolizes: we are now actually developing models in the
AnyScript language, and the system is functioning in its new state.
Click the picture to see the AnyScript text that defines the model. |
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2-D Bicycle Model
This is a 2-D
animation (643 kBytes) of a bicycle model (click the picture). It has a
certain sentimental value to the project participants, because this was
the example that really got the project started.
The example also
has a special status inside the AnyBody code. It was created before the
general modeling facilities were available, and the kinematics of bones
and muscles is therefore hard-coded, and this remains a special section of
the AnyBody system. A 3-D bicycle model using the general modeling
facilities has been developed (see further below) and will eventually
replace this model completely. |
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Optimization of a squat jump
A squat jump is a classical example of biomechanical
simulation. It is similar to a number of practical movement cases in the
sense that the overall goal is clear - to lift the center of gravity as
high as possible - whereas the precise way to accomplish this task by
means of muscle activation is unknown.
This example demonstrates how AnyBody can identify such partially
unknown motions by optimization of a performance criterion. |
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3-D Cross Country Skiing
Click the picture to see an animation of an arm, shoulder, and torso
driving a ski pole during cross country skiing (482 kBytes). This model
was largely developed by Ingrid Hartung and Janulf Sjöström, two
excellent graduate students of the Mid
Sweden University in Östersund in Sweden. They were the first
external users of AnyBody and suffered all the pain of working with an
unfinished and not very user-friendly, experimental piece of software.
Their efforts inspired us a lot in terms of required system improvements.
The model shown on
the first picture was developed at the project's workshop in Åre. It
is in an incomplete state and not physiologically correct, but it
illustrates nicely the development of the system from the initial 2-D
bicycle.
It is a model of a trunk fixed to the ground with an arm and a skiing
pole attached. The model drives the motion of the hand so that the pole
performs a cyclic motion.
The representation of the body segments is rather primitive and
requires some explanation: the centers of gravity (CG) of each segment are
represented by the yellow boxes. From the CG, the system generates a line
connected to each of the points defined on each segment, for instance for
muscle attachments. This means that the yellow lines in the model are not
skeleton representations but merely a way to illustrate rigid bodies.
The model is equipped with 52 individual muscles.
The second picture links to a model with improved motion, although we
found that it could not become entirely realistic in the absence of
scapular-thoracic motion in the model. Another important problem is that the muscle model of this stage could not handle muscles that wrap over
bones, so all muscles are approximated by straight lines. This is a
significant approximation, particularly w.r.t. the muscles spanning the
trunk.
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3-D Cycling
This effort serves a number of purposes:
 | To extend the 2-D bicycle model to three dimensions and eventually
do away with the old, hard-coded 2-D model. |
| To initiate the development of a general leg model that can serve
other purposes as well. |
| To test the use of muscle wrapping and serve as an example of a
paper on that subject. |
The video clearly shows how the gluteus maximus is wrapping over a
set of lines that create a near-cylindrical surface.
The knee, however, is more interesting. The quadriceps tendon wraps
over a single line at the knee, but the line moves with the knee and
produces a moment arm for the quadriceps that approximates the moment arm
created by the complex kinematics of a real knee.
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Car driver
This model was developed as a demonstration of the AnyBody system for
use in ergonomic design of driver spaces in cars. It is a preliminary
un-validated, un-calibrated model for demonstration purposes only. When
equipped with a better shoulder, it should capture the working conditions
of a car driver well, though.
The model is special in the sense that it comprises more than 100
muscles. It still analyses and animates quickly on a small PC.
Another interesting property is that it confirms the notion that
awkward working positions generate antagonistic muscle activity. Click
here for details.
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Exercise machine
This model is the first attempt to use our full shoulder model. It
contains all the bones and joints of the shoulder modeled with their
correct mutual degrees of freedom and driven by all the important muscles.
The main problem of the model is lack of correct anthropometrical data of
the muscles. The values used are the best we could estimate from
information in the literature.
This use of the model is for optimization of an exercise machine for
maximum isolation of its effect to the latissimus dorsi muscle. The result
will be presented at the 4th World Congress of Structural and
Multidisciplinary Optimization in Dalian, China, June 2001. The extended
abstract is available from the list of
publications. Please notice that this is ongoing work. |
(Click to enlarge)
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Bicycle spring optimization
It is possible to use the AnyBody Modeling System as a subroutine for
external software. This is a useful mechanism for doing ergonomic
optimization. This example illustrates how the technology can optimize the
configuration of springs on a bicycle crank mechanism to entirely eliminate
the top and bottom dead centers. Click here to
read more |
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