Quadruped Robot Hopping on Two Legs

This paper presents a control strategy for quadruped robots to hop on their rear legs in three-dimensional space. The proposed approach generates nominal center of mass (CoM) trajectories based on a template spring-loaded inverted pendulum (SLIP) model. Tracking this reference remains a challenge du...

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Bibliographic Details
Published in2021 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) pp. 7448 - 7455
Main Authors Li, Shenggao, Chen, Hua, Zhang, Wei, Wensing, Patrick M.
Format Conference Proceeding
LanguageEnglish
Published IEEE 27.09.2021
Subjects
Legged locomotion
Mathematical models
Quadrupedal robots
Riccati equations
Robustness
Torso
Trajectory
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Summary:This paper presents a control strategy for quadruped robots to hop on their rear legs in three-dimensional space. The proposed approach generates nominal center of mass (CoM) trajectories based on a template spring-loaded inverted pendulum (SLIP) model. Tracking this reference remains a challenge due to the underactauted nature of balance with point feet. To address this challenge, a control-Lyapunov function based quadratic programming (CLF-QP) controller is proposed, which modulates nominal ground reaction forces (GRFs) to balance the torso while considering friction limits. The CLF construction is guided by a variational-based linearization (VBL) applied to a reduced-order single-rigid-body (SRB) model, and treats underactuation via solving a Riccati equation to obtain the CLF. A new balance control approach is presented that effectively decouples sagittal plane control (via re-planning) with lateral and rotational control (via the CLF and VBL). The proposed approach shows more robust balancing performance than the conventional CLF-QP approach. Simulations of the Mini Cheetah demonstrate in-place hopping with up to a 0.71m apex height.
ISSN:2153-0866
DOI:10.1109/IROS51168.2021.9636120