Lift-up Motion Generation of Nursing-care Assistant Robot Based on Human Muscle Force and Body Softness Estimation

In our research center, we have developed a nursing-care assistant robot. This robot can lift up and transfer patient between bed and wheelchair using two human like arms. In this research, in order to generate comfortable lift-up motion automatically for this robot, we proposed a new method by reducing patient's load and pain feeling during lifting-up. We developed a musculoskeletal model to estimate muscle force, which shows the load of human body. A stiffness sensor was also developed to measure the softness distribution of human body. Contact human body on soft place can make people feel less pain. In simulation, we estimate human posture and comfortable robot motion by minimizing muscle force and contacting human body on the softest places. In experiments, the measured subjects' postures were compared with the estimated value using the estimated motions. Measured postures were very close to simulation, which shows the effectiveness of proposed method.