Recently, humanoid robots have widely researched, and they have become possible to be controlled robots with complicated kinetic characteristics. However, in the cases that the robot walks on an unknown undulating road or receives disturbances such as collision with an object from the outside, the robot loses stability and falls even if the inverted pendulum model is used. In this paper, an impedance control of a swing leg and a PI control of the rotation of a humanoid robot's waist are used to stabilize the dynamic walk on the unknown undulating road. For an impedance control, force sensors on the soles of the humanoid robot are used to measure the torque and force of a swing leg that collide with the unknown undulating road. An angular velocity sensor and acceleration sensor in the body of the humanoid robot are used to measure the rotation of the waist and its error signal are used for the PI control of humanoid robot motion. As a result, it has been confirmed that the humanoid robot can walk on an unknown undulating road with proposed walking method.
