An apparatus called a "personal motion platform" (PMP) is undergoing development for use in adding the sensations of motion to computer-controlled simulated environments of the type now popularly known as virtual reality. The PMP was conceived originally for training an astronaut to interact with surrounding objects in a simulated zero-gravitation environment; it also has obvious potential for use in a variety of applications in biomedical research, education, and entertainment.

The Reclining Chair Pitches, Rolls, and Heaves as it holds the occupant in a minimal-stress posture intermediate between the neutral body posture of zero gravitation and a normal posture of relaxation on a flat, level surface. Linear electric motors at the base of the chair drive the motion.

The PMP (see figure) includes a chair that supports the occupant in a modified version of the neutral body posture of zero gravitation. The chair is supported by a three-degree-of-freedom system of linear electric-motor actuators. A computer commands the actuators to produce the desired synthetic motions, which are reminiscent of computer-controlled motions of aircraft cockpit flight simulators. The PMP is also equipped with hand-operated controls.

The motion commands for actuators are computed partly from a combination of (1) a mathematical model of the synthetic environment, (2) the kinematics of the chair, and (3) position feedback. In addition, to enhance the interaction between the user and the synthetic environment, motion commands can be derived from simulated collisions with objects and from the hand-operated controls. As in the case of flight simulators, the computed motions are adaptively filtered to retain as much as possible of acceleration frequency components needed for realistic sensations of motion while limiting overall excursions to avoid hard stops at the limits of the actuators.

This work was done by Brian Park of Flogiston Corp. for Johnson Space Center . For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp  under the Machinery/Automation category. MSC-22623


NASA Tech Briefs Magazine

This article first appeared in the August, 2000 issue of NASA Tech Briefs Magazine.

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