Abstract
Quadruped animals achieve agile and highly adaptive locomotion owing to the coordination between their legs and other body parts, such as the trunk, head, and tail, that is, body–limb coordination. This study aims to understand the sensorimotor control underlying body–limb coordination. To this end, we adopted sprawling locomotion in vertebrate animals as a model behavior. This is a quadruped walking gait with lateral body bending used by many amphibians and lizards. Our previous simulation study demonstrated that cross-coupled sensory feedback between the legs and trunk helps to rapidly establish body–limb coordination and improve locomotion performance. This paper presented an experimental validation of the cross-coupled sensory feedback control using a newly developed quadruped robot. The results show similar tendencies to the simulation study. Sensory feedback provides rapid convergence to stable gait, robustness against leg failure, and morphological changes. Our study suggests that sensory feedback potentially plays an essential role in body–limb coordination and provides a robust, sensory-driven control principle for quadruped robots.
Highlights
Quadrupeds freely locomote in their natural habitat with great agility and efficiency
The left fore and right hind legs lift from the ground, and the other legs are anchored on the ground
Unlike most previous works based on central pattern generator (CPG) with inter-oscillator couplings (Ijspeert et al, 2007; Crespi et al, 2013; Yin et al, 2016; Ijspeert, 2020), or on gait patterns based on geometric mechanics (Zhong et al, 2018), our model uses sensory-couplings through bidirectional feedback between the legs and trunk (Figure 2A)
Summary
Quadrupeds freely locomote in their natural habitat with great agility and efficiency. Sprawling locomotion in vertebrate animals is controlled by a distributed neural network called the central pattern generator (CPG) and sensory feedback from peripheral nerves, according to experiments with salamanders (Cabelguen et al, 2003) Based on these findings, several neural network models have been proposed for sprawling robots to emulate and investigate sprawling locomotion (Ijspeert et al, 2007; Harischandra et al, 2011; Crespi et al, 2013; Yin et al, 2016; Zhong et al, 2018). The results show a tendency similar to that of the simulation This suggests that cross-coupled sensory feedback potentially plays an essential role in body– limb coordination. It could be a useful concept for designing decentralized and robust controllers for quadruped robots.
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