Inverse Kinematics of the Human Arm
MANY
CURRENT AND FUTURE AEROSPACE APPLICATIONS of Virtual Environment Technology
require that participants be represented to others (and, perhaps, to themselves) as a
graphical model, often known as an avatar. The avatar is a synthetic human figure that is
controlled, wholly or in part, by a real human. The usual process by which this is done
involves the use of position/orientation tracking devices attached to the human. Typical
applications in current use may make use of a tracking device attached to every segment of
the human body. Thus, the human may be required to wear as many as 100 individual tracking
devices. One way to reduce the number of tracking devices required is to use the known
dimensions and motion constraints of the human body to infer, from a small number of body
segments being tracked, the position of all untracked segments. Inverse kinematics allows
the computation of the location and orientation of untracked body segments from only a few
tracked segments.
AVATAR—Humans carry out functions that are imitated by a synthetic human figure
known as an avatar. Bowen Loftin adjusts a tracking device on the head of a human subject
who will direct actions of the avatar. The human body can be modeled as a structure
consisting of a series of rigid links connected at the joints.
A human body, or any part of it, can be modeled as an articulated figure structure that
consists of a series of rigid links connected at joints. The number of degrees of freedom
of an articulated figure is the number of joint angles necessary to specify the state of
the structure. If all the joint angles are known or specified, the coordinates of the end
of a limb, called the end-effector (such as the hands and feet), can be easily computed
(forward kinematics). In developing inverse kinematics, one is interested in finding the
joint angles from a knowledge of the end-effector's coordinates. Goal-directed movement,
such as moving a hand to open a door or placing a foot at a specified location on the
ground, requires the computation of the inverse kinematics, which solves for the set of
joint angles from the end-effector's location and orientation. Usually, the forward
kinematics function is highly nonlinear, rapidly becoming more and more complex as the
number of links increases; thus, the inversion of the function soon becomes impossible to
perform analytically.
The inverse kinematics problem tackled in this project is human arm modeling. Based on
work done in the first year, the complete inverse kinematics problem for the human arm has
now been implemented using neurophysiological data, producing natural looking arm postures
while executing, on common computers, faster than typical human arm motion.
Products
- A technical paper has been completed and submitted for review to an archival journal.
- The work done in this project has been utilized to support a research project, funded by
NASA-JSC, that is developing applications for astronaut training for the International
Space Station. These applications are designed to enable trainees, at different physical
locations, to share the same virtual space in order to train to perform collective tasks.
The inverse kinematics developed in this project allow participants to wear a minimum
number of tracking devices (in this case one for each hand, one for the head, and one for
the torso) in order to obtain accurate representations of their actual hand/arm positions.
SEATING—Chairs designed by UH researchers to simulate motion and activity in space
require intricate electronic components.
| Investigative Team UH PI: R. Bowen Loftin,
Ph.D., Professor, Computer Science
bowen@uh.edu
JSC PI: James C. Maida, Ph.D., Graphics Research & Analysis Facility
james.c.maida1@jsc.nasa.gov
UH Post-Doctoral Fellow: Jian Yang, Ph.D., Computer Science |
Contents
ISSO -- Institute for Space Systems Operations
1997-1998 Annual Report
