Dynamic Model of an Astronaut Equipped with a Manned Maneuvering Unit in Virtual Reality

Abstract

A virtual reality simulation system for a manned maneuvering unit (MMU) and a training system for an astronaut space walk is introduced. The system can simulate an astronaut’s outer space walk by means of manipulating the MMU, and it also can be used as a training environment by taking advantage of virtual reality properties of imagination, interaction, and immersion. As in microgravity space, an astronaut’s moving limbs cause changes in the MMU posture; these changes result in great offsets to correct direction and have a great effect on the MMU’s manipulation performance. A multibody astronaut model is developed by using relative coordinates according to the motion characteristics of an astronaut equipped with MMU. Motion information on the user’s limbs are captured by means of a motion capture subsystem and are mapped to an astronaut in virtual environment to simulate the astronaut’s limb motions while the astronaut is navigating in outer space. It is an open-chain system for an astronaut multibody model. As an astronaut can control his limbs, the whole system dynamics is a hybrid forward and inverse dynamic problem. Recursive dynamic formulations of a previous method are introduced to solve the forward dynamic problem. For the inverse dynamic part, because the system can get motion characteristics of parts of the relative coordinates, unknown generalized driving forces are applied on these known relative coordinates. All the unknown generalized driving forces and unknown relative coordinates can be combined in a set of hybrid dynamic formulations based on a forward dynamic formulation. The motion characteristics of an astronaut multibody model can be obtained by solving the hybrid formulations. Finally, some simulation results for astronaut forward-flying mode with moving limbs are presented; these results show that the movement of an astronaut’s limbs has great effects on astronaut navigation and MMU manipulation performance. The multibody astronaut model has the capability of simulating real space walk with an MMU equipped astronaut.