Assessing the effect of vibrotactile feedback during continuous multidirectional platform motion: A frequency domain approach

This study uses frequency domain techniques to demonstrate the effect of vibrotactile feedback during continuous multidirectional perturbations of a support platform. Eight subjects with bilateral or unilateral vestibular loss were subjected to two-axis pseudo random surface platform motion while donning a multi-axis feedback balance aid that mapped body tilt estimates onto their trunks via a 3-row by 16-column array of tactile vibrators (tactors). Four tactor display configurations with spatial resolutions ranging between 22.5?? and 90??, in addition to the tactors off configuration, were evaluated. Power spectral density (PSD) functions of body sway in the anterior-posterior (A/P) and medial-lateral (M/L) directions were computed at frequencies ranging from 0.0178 Hz to 3.56 Hz. Transfer functions between the platform motion and body sway were also computed. Vibrotactile feedback produced significant decreases in A/P and M/L spectral power, decreased transfer function gains up to a frequency of 1.8 Hz and 0.6 Hz in the A/P and M/L directions, respectively, and increased phase leads above 0.3 Hz. The lack of a consistent difference among tactor configurations argue in favor of the simplest 4-column configuration during multidirectional continuous surface perturbations.