Continuous Movement Tracking Performance for Predictable and Unpredictable Tasks with Vibrotactile Feedback

The purpose of this paper was to determine human movement tracking performance in response to vibrotactile feedback tracking for predictable and unpredictable continuous movement tasks. Thirteen subjects performed elbow flexion/extension and knee flexion/extension continuous movement tracking tasks while receiving tactile stimulation proportional to limb joint position error. Subjects followed 0.2-2.0 Hz desired movements for predictable tasks (single sinusoid) and unpredictable tasks (combination of three sinusoids). Tactile stimulation reaction times at the forearm to induce elbow flexion/extension and at the shank to induce knee flexion/extension were also recorded. Results of frequency tracking showed that 100 percent of participants correctly tracked unpredictable tasks at all frequencies, but only 60-80 percent of participants correctly tracked predictable tasks at frequencies less than 1 Hz and only 20-60 percent of participants correctly tracked predictable tasks at frequencies greater than 1 Hz. Subjects had less phase lag for predictable tasks than for unpredictable tasks. Reaction times at the forearm were 379 ms and at the shank 437 ms. These findings suggest that continuous vibrotactile feedback based on position errors may not be the most effective means of training higher frequency human movements and serve to inform future vibrotactile feedback design related to training human limb movements for predictable and unpredictable tasks.