Balance prosthesis based on micromechanical sensors using vibrotactile feedback of tilt

A prototype balance prosthesis has been made using miniature, high-performa nce inertial sensors to measure lateral head tilt and vibrotactile elements mounted on the body to display head tilt to the user. The device has been used to study the feasibility of providing artificial feedback of head tilt to reduce postural sway during quiet standing using six healthy subjects. Two vibrotactile display schemes were used: one in which the individual vib rating elements, called tactors, were placed on the shoulders (shoulder tac tors); another in which columns of tactors were placed on the right and lef t sides of the trunk (side tactors). Root-mean-square head-tilt angle (Tilt ) and center of pressure displacement (Sway) were measured for normal subje cts standing in a semi-tandem Romberg position with eyes closed, under four conditions: no balance aids; shoulder tactors; side tactors; and light tou ch. Compared with no balance aids, the side tactors significantly reduced T ilt (35%) and Sway (33%). Shoulder tactors also significantly reduced Tilt (44%) and Sway (17%). Compared with tactors, light touch resulted in less S way, but more Tilt. The results suggest that healthy normal subjects can re duce their lateral postural sway using head tilt information as provided by a vibrotactile display. Thus, further testing with balance-impaired subjec ts is now warranted.