Sensorimotor performance and haptic support in simulated weightlessness

Abstract

The success of many space missions critically depends on human capabilities and performance. Yet, it is known that sensorimotor performance is degraded under conditions of weightlessness. Therefore, astronauts prepare for their missions in simulated weightlessness under water. In the present study, we investigated sensorimotor performance in simulated weightlessness (induced by shallow water immersion) and whether performance can be improved by choosing appropriate haptic settings of the human–machine interface (e.g., motion damping). Twenty-two participants performed basic aiming and tracking tasks with a force feedback joystick under water and on land and with different haptic settings of the joystick (no haptics, three spring stiffnesses, and two motion dampings). While higher resistive forces should be avoided for rapid aiming tasks in simulated weightlessness, tracking performance is best with higher motions damping in both land and water setups, although the performance losses due to water immersion cannot be compensated. The overall result pattern also provides insights into the causal mechanism behind the slowing effect during aiming motions and decreased accuracy of tracking motions in simulated weightlessness. Findings provide evidence that distorted proprioception due to altered muscle spindle activity seemingly is the main trigger of impaired sensorimotor performance in simulated weightlessness.

Sensorimotor impairment and haptic support in microgravity

“… There is a clear convergence of findings of the current study and the cited underwater study, where the same tracking experiment was conducted in simulated weightlessness induced by shallow water immersion (Weber et al. 2020 ). Re-analyzing the data of this study, revealed similar impairments of motion smoothness (path length) during water immersion which were mainly evident for the sagittal motion plane.…”

“…The main findings of this control study are: (1) horizontal tracking performance is worse than vertical tracking, probably due to the worse stabilization when rotating the forearm in the transverse motion plane [see Weber et al. ( 2020 )]. (2) Higher stiffnesses and damping significantly reduce tracking error for the horizontal tracking task.…”

“…The haptic settings were the same we used in prior studies (Weber et al. 2020 ; Lange 2014 ). Since there were three subjects in the main study and three different haptic categories (stiffness, damping, virtual mass), a Latin Square design was utilized.…”

“…Indeed, the authors (Weber et al. 2020 ) could document that the positive effect of motion damping is also evident when performing tracking tasks in simulated weightlessness (induced by shallow water immersion). More interestingly, the same study also provided evidence that the sensorimotor impairment in weightlessness was mainly due to distorted proprioception and can be mitigated by applying low spring stiffness.…”

“…The present study is based on the findings of the recently conducted underwater study (Weber et al. 2020 ) and investigates manual tracking performed at different phases of a space mission using a joystick with similar haptic settings (no haptics isotonic, four stiffnesses, two dampings, three virtual masses). Based on the considerations and evidences above, we formulated the following hypotheses:…”