How to use computer manikins and motion capture

Abstract: This thesis is the result of a project that was performed at Chalmers
University of Technology in Gothenburg, during the spring of 2004.

A computer manikin is a computer model of a human body. Computer manikins
are mainly used to evaluate the use of products and workplaces. There are
different ways to manipulate a manikin. The most common way is to use
keyboard and mouse, a method that could be complicated and time consuming.
Other ways to manipulate the manikin is to use motion capture equipment, a
system where the manikin is manipulated by sensors attached to the real
human, or other Virtual Reality devices to record the motions.

The purpose of this thesis is to develop and verify a method that describes
how to use the motion capture system MotionStar, to manipulate the computer
manikin Jack. This method is presented in an easily read manual.

To find a method for the manual three problems that needed to be solved
were identified: how to measure the anthropometry, how to place the sensors
and how to fasten the sensors.

Three sets of tests were conducted to find solutions to these problems. The
method of each test evolved from findings in previous tests.

The next step was to perform a series of verifying tests. At first we
assured that our method could be used in real work applications. Three
cases were developed to resemble different work situations from a car
manufacturing company. These cases laid the foundation to a comparison
study where we compared our motion capture method with the method using
mouse and keyboard, used by simulation engineers at the car manufacturer.

The methods were compared regarding how precise the results were and how
fast they could be achieved. The second verifying test was conducted as a
usability test where the manual was tested on one test subject.

The result from the first verifying test show that there are advantages and
disadvantages regarding time usage and precision with our motion capture
method compared to the method used by the simulation engineers. Regarding
to precision one advantage with using motion capture is that it is very
easy and takes little time to make pictures of the manikin. This can be
used to freeze more than one posture in a motion sequence.

One disadvantage with our motion capture method is that the accuracy is not
precise. This is due to environmental distortions and that the
manikins do not take in account minor motions like finger movements, that
is, unless Virtual Reality Gloves are used. The main advantage with the
method used by the simulation engineers is that it visually seems to have a
higher level of accuracy.

Disadvantages with the method used by the simulation engineers are that the
posture may be inaccurate since the user has to estimate how to perform the
task, it is time consuming and only one picture of the critical end
position is made.

Regarding time usage when manipulating the manikin into static postures, it
is difficult to say which method that is preferable, since no method took
less time than the other. However, the motion capture method have one
advantage concerning time usage since the time it takes to measure the
human body and transfer this data to the computer can be left out the next
time a test is made. In view of that, the motion capture method has
potential to be much faster as long as the same test persons are used
several times.

In the comparing study only static images were created and compared. The
actual advantage however with using motion capture is that not only
critical end positions are looked upon but that motion capture can be used
to view complete motion sequences.

The result of the usability test showed that only a few adjustments had to
be made in the manual to make it easy to read and understand.

In the paper copy of this thesis a CD is attached. The content of this CD
could not be published here, but can be found and downloaded on
http://meatballs.kicks-ass.org/anna_guest in the catalouge CD. Username and
password to this site are guest and titanic.