Pseudo-somatosensory feedback about joint´s angle using electrode array

This paper proposes a presentation device of leg-information with a pseudo-somatic sensation feedback for paraplegic patient by using an electrode array. Current powered exoskeletons actually help the patient´s walk. However, they cannot perceive leg-information such as leg posture, foot-ground contact state, joint angles, and so on. Besides, the patient with the powered exoskeleton cannot walk naturally like healthy person because he/she needs to keep watching his/her lower limbs to walk safety. To achieve a walk like healthy person, we propose a presentation device which presents a pseudo-somatic sensation of lower limbs to the fingers by using an electrode array. At first, we measured human spatial resolution on a middle finger and set the distance between two stimulation points of our device. In this time, relative hip joint angles (0-41 degrees: the angles are defined relative angles between a right and left hip joint.) are presented to a middle finger with our device which has 10 or 22 stimulation points. We assigned 4.55 or 1.95 degrees to a distance of two electrodes and set the stimulation points for describing a straight or curved line such as U-shape. In order to evaluate an accuracy of the device, we conducted an experiment by comparing projected relative hip joint angles on a computer screen with measured joint angle of a finger using a finger-mounted walk controller. As result, our new device which has 22 stimulation points has a high angular resolution for presenting the angles by comparing with our previous device and can contribute to feedback of leg-information.