Abstract: Patient transfer, such as transferring a bedridden care receiver from a bed to a wheelchair or a pedestal pan and back, is one of the most physically challenging tasks in nursing care. It is the direct reason that causes most of the caregivers working in care facilities to suffer from chronic lumbar diseases. A few kinds of transfer lifts have been commercialized to solve the problem, but they are rarely used because they are time-consuming and difficult to handle. Imitating the motion when a person holds another person on his/her back, a prototype nursing-care assistant robot is developed to conduct the patient transfer. Based on the measurement of human motions including back-chest touching, leaning forward, holding up, moving and putting down, the key factors that may influence safety and comfort of the patient is analyzed and a new type of robot is designed. The robot consists of a chest holder which has three degrees of freedom and moves like a human back. This work states the details of motion design and related kinematic/dynamic analysis of the robot and demonstrate its effect on patient transfer. Experiments has been performed on eight subjects and it is demonstrated that the robot can transfer a subject from a bed to a chair and back. The force between the care receiver and the robot during transfer is the direct factor affecting the feeling of the care receiver. The robot can adapt to various care receivers with different height and weight by adjusting the motion trajectory of the chest holder.

Key words: nursing-care robot, bionic piggyback motion, patient transfer, comfortableness