Sitting motion assistance on a rehabilitation robotic walker

In our current research, we are developing a robotic walker system with standing, walking and sitting assistance function. Our developing system is based on a walker which is popular assistance device for aged person in normal daily life and realizes the standing and sitting motion using the support pad which is actuated by novel assistance manipulator mechanisms with four parallel linkages. In this paper, we develop the sitting assistance scheme which realizes the natural sitting motion based on the opinions of nursing specialists. Many previous works says the sitting motion is “reverse” motion of standing. However, in our preliminary experiment, the results of questionnaires by elderly subjects deny this finding. Thus, it is important to realize the sitting assistance without “reverse” motion of standing. Our key ideas are two topics. One topic is analysis of assistance condition which realizes a natural sitting motion by nursing specialists. The other topic is proposal of a sitting assistance control which combines force and position control. According to the patient's posture during sitting motion, our proposed control system select more appropriate control method from them. Using proposed control, our system reduces the patient's load and maintains his posture stably during a sitting motion recommended by nursing specialists.