COM motion estimation of a Humanoid robot based on a fusion of dynamics and kinematics information

A novel Kalman filter to estimate the center of mass (COM) of a Humanoid robot is proposed. In the conventional works, COM was estimated by some methods. First one is the kinematics computation based on the mass property of the robot and the global position and attitude of the body frame, but those errors degrade the estimation accuracy. Second is the double integral of COM acceleration computed by the measured external force. However, its accuracy suffers from the error accumulation with the integration and the initial error remains. Third is based on the relationship between COM and the zero-moment point (ZMP), but it ignores the torque around COM. Additionally, it only dealt with the horizontal movement. For those problems, the proposed method combines those informations in order to improve the accuracy. Particularly, in order to estimate three dimensional motion of COM, the proposed method reduces the offset included in the vertical component by utilizing the interference between the horizontal and vertical component of COM shown in third information. Through the simulation, the improvement by the proposed method is verified.