Vibrotactile Sensory Feedback System for Upper Limb Amputees

Although during the last decades, the dexterity of active myoelectric-controlled prosthesis has made significant progress, there is still no or very limited sensory feedback in the commercial prosthesis. Sensory feedback is important for active prosthesis users because it can not only increase grasping performance but also introduce an embodiment feeling to the amputee user. There has been some research focused on providing non-invasive sensory feedback to amputees because non-invasive feedback has higher user acceptance, compared to invasive ones. For non-invasive sensory feedback, vibrotactile was widely used for its relative small size, light weight, and low power consumption. A sensory feedback system were designed, incorporating pressure sensors, wireless communication modules, and a non-invasive haptic display. The flexible skin made of TangoBlack was attached to the robotic hand. Five miniaturized pressure sensors were embedded in the skin, one on each finger. The sensed pressure data were transmitted by custom-designed wireless communication modules to the haptic display control module. The sensory feedback was delivered by five pancake-shaped eccentric rotating mass (ERM) embedded in the socket. The distribution of ERMs corresponds to the shape of the phantom fingers. The vibrational amplitude was proportional to the sensed pressure. This system was tested on one amputee with phantom map. The finger identification test and handling fragile objects task were conducted. For the first one, the amputee was blind folded and wearing a headphone to eliminate visual and audio cues. The experimenter pressed the robotic finger and the subject answered which finger he felt being touched. The amputee could answer all the fingers correctly for all the trials. Then the subject was asked to grasp eggs and move them to a small basket. The amputee could move all the eggs without dropping or breaking any. There were no detectable interference between the feedback and EMG sensors.


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