Development of the Wearable Device to Measure a Floor Reacting Force

The objective of this study is to measure a floor reacting force by the wearable device. We attached six pressure sensors under a sole and created the estimating equation of floor reacting force using the sensor outputs by the data stepping on a force plate. Estimation was tried by the stepping motion and a normal gait. We tried four types of estimating equation: multiple coefficients or a single coefficient and individual or general, respectively. As a result, the errors were minimum during the expecting motion with multiple and individual coefficients. However, the errors increased too much during unexpected motions. In case of such motions, estimation with a single coefficient would rather better. Moreover, using the general estimating equation for any test subjects, estimation with multiple coefficients could not reduce the errors much relative to the case with a single coefficient. These results indicated that using many explanatory variables might be good for a limited condition, however, a few variables might be enough for covering a wide range of situations, motions or test subjects. After all, using a generalized estimating equation, the estimation error was about 20kgf on average, which is too large for using on rehabilitation. Our future plan is to reduce the errors by using individual parameters or using multiple formulas determining which one is proper to use automatically.