Development of a Supine Pseudo-Walking Rehabilitation Robot Capable of Multimodal Sensory Feedbacks during Limb Manipulation

In the acute phase of stroke, it is important to promote functional recovery of the central nervous system by issuing motor intentions and performing repetitive movements. To facilitate early walking practice in the acute phase, we have developed what we term a “supine pseudo-walking rehabilitation robot” that can perform walking training in the supine position. This robot is capable of multimodal feedbacks consisting of somatosensory feedback by following a walking trajectory, plantar vibration feedback that gives the sensation of load transfer during walking, and visual feedback in a virtual reality (VR) space. The somatosensory feedback is created by moving the patient's lower limbs in such a way as to reproduce the walking trajectory of a healthy subject, by means of a link mechanism. The feedback for plantar vibration, which gives the sensation of load transfer during walking, was generated by vibration motors which vibrate under first the heel and then the toe in accordance with the walking phase. We built a prototype of the supine pseudo-walking rehabilitation robot, and then evaluated whether it could produce the sensation of natural walking using these feedbacks by the experiments on healthy subjects, and found that it was possible to obtain the sensation of natural walking with the supine pseudo-walking robot alone. The results also suggest that the use of visual feedback and load-shifting sensory feedback can improve the sense of natural walking. In addition, when we evaluated how changes in muscular effort either appeared or did not appear when mismatch errors in different types of multimodal feedbacks were presented, a significant increase in EMG potentials was observed in two of the seven conditions. This suggests that it is possible to influence patient motor effort changes by manipulation of the multimodal feedback.