The role of auxiliary and referred haptic feedback in myoelectric control

The use of haptic display to refer cues sensed electronically from a prosthetic terminal device promises to improve the function of myoelectrically controlled upper limb prostheses. This promise is often evaluated in experiments involving non-amputees, though the availability of additional haptic feedback from an intact hand (auxiliary feedback) may confound attempts to use non-amputees as stand-ins for amputees. In this paper we test the influence of auxiliary haptic feedback on myoelectric control performance by introducing various grasp conditions in a compensatory tracking task. We ask non-amputees to compensate for the motion of a random signal by producing myoelectric control signals with a hard object, soft object, or no object (requiring co-contraction) in their grasp. The error signal is displayed through a squeeze band worn about the upper arm or a visual display. Our results suggest that the main difference between tracking with haptic and visual feedback is low-frequency drift, and that auxiliary feedback does not substantially influence task performance. Despite the drift, our results show that participants are able to respond to cues presented through the squeeze band in the compensatory tracking task.