3DZMP-based control of a humanoid robot with reaction forces at 3-dimensional contact points

Expectations for the practical use of service robots have increase of the acceleration of demographic aging. A humanoid robot is a promising form factor for service robots. When a humanoid robot is used in human environments, the robot must be designed considering various reaction forces that act on it. To date most walking robots use the conventional ZMP method for control in order to maintain a stable walking posture. However, the conventional ZMP method cannot handle the various reaction forces that act on contact points in three-dimensional space between a humanoid robot and the environment. To overcome this, a novel control method is proposed, comprising 3DZMP and pZMP. 3DZMP is defined as a point in three-dimensional space where the moment around all axes is zero. 3DZMP can prevent the rotation of a humanoid robot. pZMP is defined as a point where the 3DZMP is orthographically projected on a plane. pZMP is one way to evaluate the stability of 3DZMP. We implemented the proposed method with a prototype and verified that the robot could react to reaction forces, which the conventional ZMP method could not handle.