An extended inverted pendulum model giving minimal interpretation of vertical ground reaction force while a human walks

Vertical ground reaction force(vGRF) has been widely known as a qualitative features of human walking. While a human walks, the vGRF exhibits a double peak profile in which two maximal values appear from the heel contact to the toe off. So far, various studies have been mainly conducted in the field of biomechanics to elucidate the mechanism by which the double peak profile of the vGRF can be generated. In these researches, inverted pendulum models that allow the change in the length of the support leg have been considered as one of the minimal models. It is, however, known that the center of mass(COM) trajectory of human waling coincides well with the COM trajectory of the inverted pendulum with constant support leg length because changes in the length of legs during walking is small compared to the length. In this research, we propose a new minimal model for human walking based on the inverted pendulum model with fixed support leg length which can interpret the double peak profile of vGRF by considering double support phase. As a result of the verification by the numerical simulation, the proposed model was successfully confirmed that the double peak profile of vGRF can be reproduced in accordance with the COM trajectory of the inverted pendulum model with fixed support leg length.