Estimating zero moment point and floor reaction force using visual markers

Validation of locomotive functions in elderly individuals is important in aging society. An algorithm to estimate the floor reaction forces on both feet were previously developed to evaluate the locomotive functions. This study improved this algorithm so that the floor reaction forces of both the feet and the force of something in his/her hand such as a stick can be estimated. To estimate a zero moment point (ZMP) and floor reaction forces of the both feet and a stick, the position and pose of entire body and stick were measured using by a single camera and visual markers. Verification experiments were performed using a motion capture system and force plates. The results of the verification experiments indicated that the ZMP and floor reaction forces could be estimated with a high degree of accuracy. The findings also showed that the timing of an increase and decrease in the ZMP and floor reaction forces of the “stepping motion” coincided.