Digital Human Simulation for Fall Risk Evaluation When Sitting on Stepladders

Abstract

Fall accidents due to the loss of balance on stepladders never go away. Straddling and sitting on the top cap of the stepladders appears to be stable, but working in sitting may lose balance. The purpose of this study is to evaluate the fall risk when sitting on stepladders based on digital human simulation. This study consists of two steps: preliminary experiment and digital human simulation. The preliminary experiment is conducted for estimating the lumbar critical torque. In the experiment, backward tilt motion is measured by optical motion capture system with force plates. Six older people participate in the experiment. After that, the fall risk of stepladder sitting is estimated by the digital human simulation. In the simulation, various reaching postures are generated by the inverse kinematics calculation, and corresponding lumbar torque is further estimated by the inverse dynamics calculation. Our results clarify the reaching postures into falling or stable postures by comparing the measured critical torque with the estimated one.