A feasibility test of evaluation of gait movement by using center of mass estimation with inertial sensors

It is necessary to control movement of center of mass (CoM) to realize stable walking. Since CoM has been shown to reflect asymmetry of movement, energy cost and ground reaction force (GRF), it is expected that CoM position makes possible to evaluate walking ability. This study aimed at examining the possibility of using CoM in gait evaluation, in which CoM position was estimated from signals measured only with inertial sensors. In this paper, 16 m straight walking of healthy subjects was measured with 7 wireless inertial sensors, and estimated CoM positions for the steady state gait were analyzed. Amplitude of change of vertical position of CoM during gait increased as walking speed increased in all subjects. Waveform of vertical position of CoM for each gait cycle was found to be divided into 2 patterns. The difference in the waveform of vertical position of CoM was considered to involve difference in gait movement to move CoM upward, in which knee joint angle or inclination angle of the shank segment was mainly changed for the term from the double stance phase to the single stance phase. This difference was considered to show the difference in gait strategy. The results of this study suggested that vertical component of CoM position became useful to evaluate gait movements.