Muthu Govindaraj,
PhD
Professor, School
of Engineering and Textiles
Philadelphia
University
Research Projects
Project
1 Title: ITR: Representations and Algorithms for Deformable Objects.
Project
2. Title: Haptic Simulation of Fabric Hand
Project
3 Title: Objective Evaluation of Garment Comfort
Title: ITR:
Representations and Algorithms for Deformable Objects.
(Research supported
by National Science Foundation grant)
People: Muthu Govindaraj, Ashish Garg, Christopher Pastore
Fabric drape is among
the most important quality features for assessing fabric performance in apparel
and other applications. Our research focuses on establishing a generalized
model to calculate mechanical properties of fabrics with a wide range of yarn
characteristics and weave structure. We use the mechanical characteristics as
inputs to model virtual fabrics. We are working with Rutgers University
researchers (Dimitris Metaxas, Kiran Gatla and Suejung Buh) on adopting an absolute
nodal coordinate formulation Finite Element Model (FEM) for cloth. We have
earlier established fabric drape modeling method which would be enhanced considerably with the above
mentioned new approaches.
In order to validate performance of models simulating behavior of
fabrics in dynamic conditions, it is necessary to formulate new parameters.
Most important parameter would be dynamic drape. Dynamic drape has been extensively
studied by Japanese researchers Matsudaira et. al. At Philadelphia University
we have followed the work of Matsudiara et al. We have added additional
features to dynamic drape testing using our newly developed dynamic drape meter. Damping coefficient is another important input
parameter for modeling behavior of fabrics in dynamic conditions. A new method
has been developed to estimate the damping coefficient of fabrics.
Our research will
enable simulate virtual fabrics on computers which will help apparel design,
e-commerce and computer animation.
Title: Haptic
Simulation of Fabric Hand
(Research supported
by NTC)
People:
Muthu
Govindaraj and Ashish Garg
Gang Huang and Dimitris Metaxas ( Rutgers University)
Traditionally fabrics are evaluated subjectively using certain criteria
such as the thickness, softness, stiffness, smoothness and fullness of the
fabric. A combination of these properties is commonly referred to as fabric
hand. Fabric hand is an important criterion for the consumer when buying
apparel and other textile goods. Currently several research projects, including
the one mentioned above, are addressing the problem of fabric drape simulation.
Some commercial systems are already on-line where the drape of a garment can be
visualized. However, someone purchasing a garment on-line still has no sense of
the ÔhandÕ of the fabric. Our work aims to simulate fabric hand so that a
consumer would not only see a virtual garment drape but also would be able to
feel the fabric.
We initially used a device called the PHANToM¨ that uses a pen like
probe to scan a virtual surface and generate the feel of surface. The two
primary parameters required to generate a virtual surface are the frequency of
the surface profile and the friction (the drag) of the profile. These two data
sets are available from KES measurements of our fabric samples.
The PHANToM¨ is a multi-axis force feed back system. By holding a pen
with a stylus at the end of the PHANToM¨ articulated robot, and moving the pen
over a constructed surface in the virtual space, a feed back response can be felt on the hand. The
limitation of the device is that the contact with the virtual surface is over a
line.
We then developed a fabric haptic device of our own called the Philau
Haptic Device (PHD). In this device a person holding and moving a mouse over a
simulated fabric on a computer screen will have the surface profile of the
fabric rendered to his
forefinger. This is achieved through a matrix of pins. The friction
profile is conveyed by a system of electromagnetic brakes.
Both the above devices have
been evaluated by subjects and responded well in terms of distinguishing rough
from smooth fabrics.
Title: Objective
Evaluation of Garment Comfort
(Research supported by the
Laboratory for Engineered Human Protection)
People: Muthu Govindaraj and Shefali Agarwal
Comfort of a garment is
dependant on various factors including the pressure applied by a garment on the
wearer. Garment comfort can be improved by reducing the pressure imposed by the
garment on the body which in turn can be controlled by parameters such as fit,
fabric friction, fabric stretch, pattern design, etc. Garment needs to have
ease so that the wearer can perform dynamic movements without any restraints.
On the other hand, too much ease is undesirable from an aesthetic point of
view. We are making an attempt to objectively evaluate garment pressure on
human body and relate the results to subjective assessment.
In this project, we develop
a psychophysical experimental procedure for evaluating garment pressure on a
wearerÕs body. We are conducting a series of subjective and objective studies
with wearersÕ trial of a few types of garments. The correlation between wearing
pressure measured by pressure sensors and subjective parameters like pressure
sensation, feeling of stiffness, itchiness, scratchiness, softness and
smoothness will be statistically investigated.
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Figure 1: Pressure
Points
We have mounted thin film pressure sensors
at four locations on the garment as shown in the figure above. Subjects will be
asked to perform various activities like knee bending, sitting, etc. Pressures
generated on the sensors by the garment on the body during these movements are
captured. Examples of data from pressure sensors are given below:
Figure 2: Pressure
Data
Subjects are also asked to
answer a survey questionnaire after performing every activity. Survey questions
consist of psychophysical scaling used in rating subjective perception. The
subjects are asked to rate the sense of pressure on a scale of 0-10. The
results of the experiments will be used by another group of researchers to
alter garment patterns to increase comfort.