2.2 Kinematics and Dynamics To investigate the basic law in locomotion, such as trajectories of mass center and state changes during stance phase or flight phase. Such conceptions as D-H coordinates and Lagrange Formula are used in the study 2.2 Kinematics and Dynamics To investigate the basic law in locomotion, such as trajectories of mass center and state changes during stance phase or flight phase. Such conceptions as D-H coordinates and Lagrange Formula are used in the study