A novel haptic fMRI interface for five-axis force and motion neuroimaging experiments
Samir Menon, Amaury Soviche, Jananan Mithrakumar, Alok Subbarao, Oussama Khatib
Abstract
In this paper, we demonstrate that it is feasible to conduct reliable multi-axis force control motor neuroimaging experiments in humans using a novel five degree-of-freedom Haptic fMRI interface (HFI-5). We demonstrate that HFI-5 supports accurate force and torque control for all its axes. In addition, it minimizes the force-to-torque coupling induced by its closed chain kinematic structure. HFI-5 has low backdrive friction (<; 0.5N; <; 0.05Nm), which improves its haptic transparency. While the device is large and consequently flexible, a linear model can correct kinematic accuracies due to device deflection. Resulting position error measurements are similar in scale to human hand jitter, and are thus satisfactory. To test HFI-5's efficacy, we performed force perception and force discrimination tests with it on four human subjects. The test revealed that humans could readily perceive forces above 1N and could discern forces that were about 33% apart. As such, HFI-5's force range (x:±16.36N; y:±4.62N; z:±6.9N; passively gravity compensated) can support a wide variety of forces that are perceptible and distinguishable. Finally, we performed ten fMRI scans with a human subject who performed a visually guided force-control experiment. Temporal noise patterns in fMRI measurements matched the fMRI baseline (0.8%), which demonstrates that HFI-5's electromagnetic motors do not introduce substantial noise. HFI-5 is thus ready to be used in motor neuroimaging experiments.
BibTeX
@inproceedings{iros2017_anovelhapticfmri,
title = {A novel haptic fMRI interface for five-axis force and motion neuroimaging experiments},
author = {Samir Menon and Amaury Soviche and Jananan Mithrakumar and Alok Subbarao and Oussama Khatib},
booktitle = {IROS 2017},
year = {2017}
}