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Perceptual Aspects of Locomotion Interfaces
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OverviewWe are exploring fundamental perceptual issues key to our ability to construct locomotion interfaces allowing a user to walk naturally through a large scale virtual environment. If successful, such interfaces may become an important technology supporting applications including training, architectural walkthroughs, education, and entertainment. Treadmills
are an example of a locomotion
device allowing a user to walk in a relatively normal manner
without significant change in actual location. Our research deals with
combining more sophisticated locomotion devices with visual displays in
order to construct true locomotion interfaces which will allow
a user to interact with a virtual world by walking through that
world.The principal experimental device used in this research is the Sarcos Treadport. The Treadport is a custom built, computer controlled treadmill with a 6' by 10' walking surface. It is possible to either preset walking speed or to have walking speed under user control. A mechanical tether serves to both sense user position on the belt and to optionally apply forces to the user to simulate the inertial effects that would be associated with changes in speed while walking on normal ground and to simulate the changes in forces associated with walking up or down slopes in the real world. The belt itself can also be tilted under computer control. Three 8' by x 8' rear projection video screens arranged to provide a 180 degree field of view are used to provide visual input. This is a highly interdisciplinary effort, involving researchers with expertise in computer graphics, robotics, vision science, and experimental psychology. The project is centered at the University of Utah, with additional participants from the University of Minnesota, Vanderbilt University, and Mount Holyoke College. Examples of current research:Perception/action coupling in locomotion interfaces. We have achieved one of the main goals of the project by demonstrating that perception/action coupling in a treadmill-based virtual environment (treadmill VE) transfers to perception/action coupling in the real world. Previous research has demonstrated that humans calibrate their visually-directed actions to changing circumstances in their environment. Using a treadmill VE, we show that calibration of action is reflected in the real world as a result of manipulating the relation between the speed of visual flow, presented using computer graphics, and the speed of walking on a treadmill. Building on this work, we were able to investigate an open question involving human gait transitions and show that the speed of visual motion influences the speed at which the gait transition occurs. These result demonstrates both the effectiveness of treadmill-based VEs in simulating the perceptual-motor effects of walking through the real world and the value of such systems in addressing basic perceptual questions that would otherwise be difficult to explore. Interaction
between visual and biomechanical judgments of slopes. We
investigated how judgments of slant were affected by actual walking
through the terrain under view. Comparisons were made between four
situations: (1) slopes viewed without any movement through the
environment, (2) slopes viewed after passive movement through the
environment, (3) slopes viewed after walking through the environment on
the Treadport, but without the added forces associated with walking up
and down hills, and (4) slopes viewed after walking through the
environment on the Treadport with simulated hill forces. Haptic
estimations of slant, as indicated using a palm board, was accurate in
all cases. The phenomenological perception of slant was overestimated
in all cases, with the overestimation increasing when slope forces were
present.Using audition to increase presence. Research is underway on increasing the sense of presence in locomotion interfaces by providing realistic, three-dimensionally localized footfall sounds. Force Sensing Resistors (FSRs) are being employed to measure the pressure of the foot against the ground. Methods for realistically rendering the footfall sounds and for calibrating the sensors and detecting footsteps have been developed. Faculty Sarah Creem-Regehr John Hollerbach Peter Shirley William B. Thompson Graduate Students Benjamin Kunz Scott Kuhl Leah Wouters Tina Ziemek Alumni Valentina Dilda Amy A. Gooch Betty Mohler Ben Newton Peter Willemsen Collaborators Claude Fennema, Jr. , Mount Holyoke College Herbert Pick, Jr. , University of Minnesota John Rieser , Vanderbilt University Publications.. Support for this project is provided by the National Science Foundation under grant # 0121084 |
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