Online Walking Pattern Generation for Humanoid Robot with Compliant Motion Control

The compliant motion of humanoid robots is one of their most important characteristics for interacting with humans and various environments in the real world. During walking, compliant motion ensures stable contact between the foot and ground, but walking stability is degraded by position tracking performance and unknown disturbances. To address the issue of instability of humanoid robot walking with compliant motion control, this paper proposes a model for real-time walking pattern generation considering the motion control performance of a robot. The dynamic model of a robot with a motion controller is described as a second-order system approximating position tracking performance with a linear inverted pendulum model to determine the relationship between the zero-moment point and center of mass (CoM). The CoM trajectory is calculated using preview control based on the dynamics model and current state of the robot. Therefore, even if the robot has the low tracking performance due to compliant motion control, the walking stability can be ensured. The proposed method was implemented on our humanoid robot, DYROS-JET, and its performance was demonstrated through improved stability during walking.