Effects of attractive versus repulsive vibrotactile instructional cues during motion replication tasks

The Mobile Instrument for Motion Instruction and Correction (MIMIC) enables an expert (i.e., physical therapist) to map his/her movements to a trainee (i.e., patient) in a hands-free fashion. MIMIC comprises an Expert Module (EM) and a Trainee Module (TM); both modules include six-degree-of-freedom inertial measurement units, microcontrollers, and batteries. The TM also includes actuators that provide the trainee with vibrotactile instructional cues. The estimated expert body motion information is transmitted wirelessly to the trainee; based on the computed difference between the motions of the expert and trainee, directional instructions are displayed to the trainee's skin via vibrotactile stimulation. This study examined anterior-posterior trunk movements using a simplified version of the MIMIC system in which only two actuators were used to provide feedback and pre-recorded target trajectories were used to represent ideal expert movements. The study was designed to investigate the effects of attractive versus repulsive vibrotactile instructional cues when the motion speed and task complexity were varied. Preliminary results (n = 12) suggest that repulsive vibrotactile instructional cues lead to the greatest correlation between expert and subject motion, the least time delay, and the least tilt error.