This paper studies stabilizer design for position controlled humanoid robots. Stabilizers are essential for position-controlled humanoids, whose primary objective is to adjust the control input sent to the robot to enhance the performance of trackingthe planned reference trajectory.

Conventional stabilizer design techniques primarily rely on simplified bipedal models and measurement of the renowned zero moment point (ZMP). However, these simplifications limit the performance of the stabilizers due to lack of considering whole-body effects as well as the full six-dimensional contact force information. To address these issues, we develop a novel force feedback based whole-body stabilizer that fully exploits the six-dimensional force measurement information and the whole-body dynamics to improve tracking performance. Through rigorous analysis of whole-body dynamics of position-controlled humanoids under unknown contact, the developed stabilizer leverages quadratic-programming based technique that allows cooperative consideration of both the center-of-mass tracking and contact force tracking.

The effectiveness of the proposed stabilizer is demonstrated with the UBTECH Walker robot in the MuJoCo simulator. Simulation validations show a significant improvement in various scenarios as compared to commonly adopted stabilizers based on the zero-moment-point feedback and the linear inverted pendulum model.

Video link: https://www.bilibili.com/video/BV1hK411c7Ph