256 / 2021-04-15 14:49:21

Estimation of center of gravity of upper body in sitting posture using force platforms

Center of gravity,Upper body,Sitting posture,Force platform

Special Sessions > Vehicle noise, vibration and harshness: Challenge and Solution Ⅰ

Balance analysis of sitting posture is expected to be useful for diagnosis of low back pain and evaluation of ride comfort of vehicles. The ideal balance analysis requires an accurate estimation of the center of gravity (COG) of the upper body. While a typical COG estimation method uses 3D motion analysis systems, it is not practical in measuring time, space, and cost. In past studies, there are no practical COG estimation methods in sitting posture. This study aims to estimate the COG of the upper body in the sagittal plane using two force platforms. The force platforms were mounted under the buttocks and feet, and the COG position was estimated based on the equations of motion. The method can be applied when the seat moves horizontally, such as in a vehicle. To verify the accuracy of the present method, we conducted three types of experiments: rest sitting, voluntary motion, and horizontal sway of the seat. Compared with the three-dimensional motion analysis system, the present method showed high estimation accuracy in the resting sitting and voluntary motion. The result of the horizontal sway of the seat test caused minor estimation errors. To investigate the cause of the estimation error, we applied the singular value decomposition. The results implied that the head-shaking might have affected the results.