Mechanical design of a standing up assistance apparatus of leaning forward the upper body which can be transformed into a flat lying posture

An apparatus to assist elderly patients to stand up, as well as leaning forward the upper body, has been developed. The mechanism of the apparatus enables to shift the person's center of gravity along an adequate trajectory during the standing up process, so as not to cause strain on the joints of the user's leg. The apparatus also assists a person to alter from standing or sitting posture to lying posture. Although the mechanism has multiple links and joints, only one actuator is required to transform the apparatus between aforementioned three postures. The length of each link of the mechanism has been determined from their effect on the backrest angle when each link in the mechanism length is changed. The torque of the hip and knee joints while using the apparatus can be calculated and compared with the data of a user not using the apparatus. We hypothesize that the output torque of the user while standing is decreased by using the apparatus.