Trajectory adaptation of biomimetic equilibrium point for stable locomotion of a large-size hexapod robot
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Trajectory adaptation of biomimetic equilibrium point for stable locomotion of a large-size hexapod robot Chen Chen1
· Fusheng Zha1 · Wei Guo1
· Zhibin Li2 · Lining Sun1 · Junyi Shi1
Received: 11 September 2019 / Accepted: 5 November 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This paper proposes a control scheme inspired by the biological equilibrium point hypothesis (EPH) to enhance the motion stability of large-size legged robots. To achieve stable walking performances of a large-size hexapod robot on different outdoor terrains, we established a compliant-leg model and developed an approach for adapting the trajectory of the equilibrium point via contact force optimization. The compliant-leg model represents well the physical property between motion state of the robot legs and the contact forces. The adaptation approach modifies the trajectory of the equilibrium point from the force equilibrium of the system, and deformation counteraction. Several real field experiments of a large-size hexapod robot walking on different terrains were carried out to validate the effectiveness and feasibility of the control scheme, which demonstrated that the biologically inspired EPH can be applied to design a simple linear controller for a large-size, heavy-duty hexapod robot to improve the stability and adaptability of the motion in unknown outdoor environments. Keywords Equilibrium point hypothesis · Compliant-leg model · Contact force optimization · Deformation counteraction · Large-size hexapod robot
1 Introduction On discontinuous terrain surfaces, legged robots can achieve significant mobility advantages in such a challenging environment compared to wheeled types (Semini et al. 2016; Gehring et al. 2016). But by far, legged robots are still not as agile as legged animals on this planet. Stable and robust motion control of different kinds of legged robots, especially large-size legged robots, remains an important research topic to address (Li et al. 2016; Hodoshima et al. 2007; Irawan and Nonami 2011; Zhuang et al. 2017). Particularly for a largesize legged robot, the deformations of robot structure, ie body Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10514-020-09955-4) contains supplementary material, which is available to authorized users.
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Wei Guo [email protected] Zhibin Li [email protected]
1
Harbin Institute of Technology, No.92 West Dazhi Street, Harbin, Heilongjiang Province, China
2
School of Informatics, The University of Edinburgh, Edinburgh, UK
and legs, as well as the significant foot-ground impacts are not negligible and can largely downgrade the walking performance, ie motion stability and body attitude, especially on tough terrains. Compared to small-size legged robots, largesize robots have difficulty in recovering the body posture due to very large inertia, and the resulted instability may further lead to irreversible damage to the robot. Therefore, the capability of enhancing a stable motion is of cruci
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