An automatic depressurization assistance based on an unconscious body motion of a seated patient on a wheelchair

For reducing the risk of pressure sore caused by long period sitting on a wheelchair, we have been developed a depressurization motion assistance system for a wheelchair user. Our developed system consists of a sitting surface lifting device and a backrest tension coordination device. Our system assists to realize the suitable posture of the seated patient with these two devices. In our previous works, we investigate an index of the pressure sore risk by analyzing unconscious body motions of a healthy person who sits long time. From these analysis results, subjects want to depressurize their buttock or back when their posture is not suitable and a pressure concentration to a specific position on their buttock or back continues the fixed period. These conditions seem to be an index of pressure sore risk and in this paper, we propose an automatic depressurization motion assistance scheme based on this index. Our proposed system assists a patient to move his body for distributing the pressure concentration on his buttock or back and leads the suitable sitting posture when these conditions are fulfilled. Using our proposed assistance system, the patient can depressurize by a natural body motion when he wants. The performance of our system is verified by experiments using our prototype.