A 6 DOF opto-inertial tracker for virtual reality experiments in microgravity

Gravity plays a role in many different levels of human motor behavior. It d ictates the laws of motion of our body and limbs, as well as of the objects in the external world with which we wish to interact. The dynamic interact ion of our body with the world is molded within gravity's constraints. The role played by gravity in the perception of visual stimuli and the elaborat ion of human movement is an active research theme in the field of Neurophys iology. Conditions of microgravity, coupled with techniques from the world of virtu al reality, provide a unique opportunity to address these questions concern ing the function of the human sensorimotor system [1]. The ability to measu re movements of the head and to update in real time the visual scene presen ted to the subject based on these measurements is a key element in producin g a realistic virtual environment. A variety of head-tracking hardware exists on the market today [2-4], but n one seem particularly well suited to the constraints of working with a spac e station environment. Nor can any of the existing commercial systems meet the more stringent requirements for physiological experimentation (high acc uracy, high resolution, low jitter, low lag) in a wireless configuration. T o this end, we have developed and tested a hybrid opto-inertial 6 degree-of -freedom tracker based on existing inertial technology [5-8]. To confirm th at the inertial components and algorithms will function properly, this syst em was tested in the microgravity conditions of parabolic flight. Here we p resent the design goals of this tracker, the system configuration and the r esults of Og and 1 g testing. (C) 2001 Elsevier Science Ltd. All rights res erved.