Measurement of human body stiffness for lifting-up motion generation using nursing-care assistant robot — RIBA

In our research center, we have developed a nursing-care assistant robot - RIBA. This robot can lift up and transfer patient between bed and wheelchair using two human like arms. In this research, we proposed a new method to generate comfortable lifting-up motion automatically for using this robot. This method can reduce the pain feeling of patient during lift-up by setting robot arms to contact human body on the softest places. In order to measure the stiffness of soft human body, a stiffness sensor was developed, which has a large measurement range. We measured the stiffness on the back of upper body and thighs. From the measured data, we got an average stiffness distribution. In simulation, by controlling robot arm to lift human body up from the estimated softest place and minimizing the load of human body, we obtained a most comfortable robot motion. In experiment, all subjects felt this motion comfortable. The measured subjects´ postures were also very close to the estimated value, which confirmed the effectiveness of stiffness measurement and motion generation method.