  Individuals who use myoelectric upper-limb prostheses often rely heavily on
vision to complete their daily activities. They thus struggle in situations
where vision is overloaded, such as multitasking, or unavailable, such as poor
lighting conditions. Non-amputees can easily accomplish such tasks due to
tactile reflexes and haptic sensation guiding their upper-limb motor
coordination. Based on these principles, we developed and tested two novel
prosthesis systems that incorporate autonomous controllers and provide the user
with touch-location feedback through either vibration or distributed pressure.
These capabilities were made possible by installing a custom contact-location
sensor on thefingers of a commercial prosthetic hand, along with a custom
pressure sensor on the thumb. We compared the performance of the two systems
against a standard myoelectric prosthesis and a myoelectric prosthesis with
only autonomous controllers in a difficult reach-to-pick-and-place task
conducted without direct vision. Results from 40 non-amputee participants in
this between-subjects study indicated that vibrotactile feedback combined with
synthetic reflexes proved significantly more advantageous than the standard
prosthesis in several of the task milestones. In addition, vibrotactile
feedback and synthetic reflexes improved grasp placement compared to only
synthetic reflexes or pressure feedback combined with synthetic reflexes. These
results indicate that both autonomous controllers and haptic feedback
facilitate success in dexterous tasks without vision, and that the type of
haptic display matters.
