Evaluation of the manikin building function in eM-RAMSIS
when using Motion Capture

Abstract: This thesis project was formulated by Volvo Cars to find an answer to the
question if an investment in a manikin building software was necessary or
if the existing manikin eM-RAMSIS could produce valid results when using
Motion Capture data to guide it. Motion Capture is a system for recording
an objects motion and transforming it to a digital form which can be
utilized to guide the motions or postures of various digital objects, in
this case computer manikins. A computer manikin is a digital human model
and has all the characteristics of a human: joints that are restricted to
movements in only some directions, hands that can grasp things etc. These
manikins are used by Volvo Cars to simulate working postures for the
assembly workers who will work on the assembly lines of future car models.
The manikins have been positioned after the best knowledge of the
simulation engineer using mouse and keyboard. However with this new
technique it is possible to record the actual position of an assembly
worker in the Motion Capture lab.

Research conducted on the subject of Motion Capture and manikins show that
it is crucial that the manikin closely resembles the person recorded. The
manikin available for simulation engineers on Volvo Cars is eM-RAMSIS who
only has three possible adjustments: length, sitting height and
circumference. Thus the question arose whether eM-RAMSIS could produce
valid results or not.
Three tests were originally carried out to find an answer to the question.
The first test was aimed at examining the markerset used and verifying it,
the result being to stick to the original markerset of 42 markers. The
second test was designed to try to find some postures where the manikin
encountered trouble and the postures identified were further analyzed and
used as input in the design of the main test. This third test was performed
by a test group of eleven, six female and five male participants of
different anthropometry. The test consisted of different stretching and
twisting tasks. The one which caused the manikin the most problems was
reaching forward to the maximum while leaning forwards supported by a table
frame. This task was extensively analyzed, taking the manikin to a virtual
table and measuring how far it could reach and comparing this with the
values from the test session. In general the manikin reached shorter than
the test objects, in some cases up to 20 cm. Since there were many possible
sources of error in the main test it was decided to do a supplementary test
where the variables were cut down to a minimum. The position of the feet
was exactly marked out on the floor and carefully measured against the
table frame. For measuring of the reaching distance a cord with a stripe
running on it was fastened on the table frame. This making the fingertip of
the test object identified in three dimensions at the extreme of the
motion. The test object was accurately positioned on the markings for the
feet before the recording started.

The analysis of the supplementary test showed the same behavior as the
previous test: that the manikin could not reach as far as the actual
person. A measurement showed that the manikin had longer arms than the test
objects. It would appear that the manikin has some built in limitations as
to how it can move and be positioned. When reaching far a human lets the
shoulder follow the arm forwards and also twists the back to reach even
further, this behavior can not be mimicked by the manikin when using Motion
Capture data.

To be able to answer the question whether the manikin created with Human
Builder would produce better results comparing studies will have to be
performed and has not been performed since the software was not available
during the course of this thesis project. There has been no behavior
observed where it could be determined that it would not have occurred with
a more anthropometrically correct manikin.
The recommendations which will conclude this project are to do a comparison
study using manikins created in Human Builder, to utilize all settings
available for the eM-RAMSIS manikin, to unmark markers to instantly create
a better manikin posture, to move the Motion Capture cameras when using
many props to ensure a better data collection and using additional camera
views to collect more photographic material that can be used as reference
for judging the manikin posture.