Masuji Nagatoshi

Development of Sit-to-Stand Support System Using Ground Reaction Force

This paper shows our developing sit-to-stand support system using ground reaction force to operate device. Computer system control sit-to-support mechanism automatically by information of the user ground reaction force (GRF). The user of this device don’t need to operate the switch or button. This paper shows first prototype device and describe about device control rule, ex-periment results and the found problems of control, at first. Secondly, to solve these problems, experiment device for second prototype design is shown, and experiment method is described. Finally, preliminary results are shown in these experiments.

A Study of Coefficient of Friction of UHMWPE in Various Contact Conditions and Measurement of Contact Temperature.

Wear debris of ultra high molecular weight polyethylene abbreviated as UHMWPE were clarified to be a major cause of osteolysis. So the wear rate evaluation of UHMWPE has to be performed in the research of artificial joint using UHMWPE. But wear evaluation of UHMWPE requires scrupulous procedure. As the wear rate of UHMWPE is strongly correlated to the coefficient of friction, this study was designed to assess a change of the coefficient of friction for various contact conditions. It was found that the contact condition strongly affected the coefficient of friction. Furthermore contact temperature was measured by means of the infrared radiometric microscope and was compared to the lubricant temperature. Temperature rise up to about 12°C was observed in 30 minutes under a condition of the mean contact pressure p = 12.7 MPa and sliding speed 50 mm/s. There was a linear relation between contact temperature and lubricant temperature.