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Review
. 2024 Oct 15;9(10):628.
doi: 10.3390/biomimetics9100628.

Bionic Multi-Legged Robots with Flexible Bodies: Design, Motion, and Control

Xiang Li  1 , Zhe Suo  1 , Dan Liu  2 , Jianfeng Liu  1 , Wenqing Tian  3 , Jixin Wang  1 , Jianhua Wang  4
Affiliations
Review

Bionic Multi-Legged Robots with Flexible Bodies: Design, Motion, and Control

Xiang Li et al. Biomimetics (Basel). .

Abstract

Bionic multi-legged robots with flexible bodies embody human ingenuity in imitating, learning, and exploring the natural world. In contrast to rigid-body robots, these robots with flexible bodies exhibit superior locomotive capabilities. The flexible body of the robot not only boosts the moving speed and walking stability but also enhances adaptability across complex terrains. This article focuses on the innovative design of flexible bodies. Firstly, the structural designs, including artificial spines and single/multi-axis articulation mechanisms, are outlined systematically. Secondly, the enhancement of robotic motion by flexible bodies is reviewed, examining the impact that body degrees of freedom, stiffness, and coordinated control between the body and limbs have on robotic motion. Thirdly, existing robotic control methods, organized by control architectures, are comprehensively overviewed in this article. Finally, the application prospects of bionic multi-legged robots with flexible bodies are offered, and the challenges that may arise in their future development are listed. This article aims to serve as a reference for bionic robot research.

Keywords: CPG; bionic control; bionic robots; flexible body; locomotion; multi-legged robots; spine.

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Conflict of interest statement

Author Dan Liu was employed by the company Inner Mongolia First Machinery Group Co., Ltd, and author Wenqing Tian was employed by the company China FAW Group Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Bionic models of multi-legged robots with flexible bodies.
Figure 2
Figure 2
Artificial configurations of robots with flexible bodies.
Figure 3
Figure 3
(a) The coordinate system of the robot. (b) The robot structural layout expression, and examples: Stoch 2 consists of two segments, with two legs on each segment [7]. Hector is composed of three segments, with two legs on each segment [8]. SpaceClimber is comprised of two segments, with two legs on the head segment and four legs on the tail segment [9].
Figure 4
Figure 4
Some typical robots with artificial spines. (a) Kitty [31], (b) Canid [32], (c) NeRmo [33], (d) Cheetah-Cub-S [19], (e) Laika [20], and (f) QuaDRoPECS [18].
Figure 5
Figure 5
Five articulation types for robot segments: Bobcat [38], Ken [39], and Salamandra Robotica I [40], with permission from AAAS, Serval [37], and unnamed robot in [41].
Figure 6
Figure 6
Other designs for robots with flexible bodies: (a) Charlie [60], (b) Hector [8], (c) Origaker [48], and (d) unnamed robot in [58].
Figure 7
Figure 7
Sagittal plan motion models for bounding and galloping. (a) The spinal motion of a cheetah while it is galloping (figure captured from [54]). (b) Motion model with single-axis articulation. (c) Motion model with linear spring. (d) Motion model for asymmetric gait.
Figure 8
Figure 8
Discontinuous walking motion sequence. The numbers 1−6 in the figure indicate the sequence of discontinuous walking motion.
Figure 9
Figure 9
Distributed control with cross-coupled sensory feedback.
Figure 10
Figure 10
Hierarchical control architecture.
Figure 11
Figure 11
CPG oscillation model control. Figure captured from [40] with permission from AAAS. The meanings of the various parts in the figure can be found in reference [40].
Figure 12
Figure 12
A section of Walknet showing two leg controllers. Figure modified from [133].
See this image and copyright information in PMC

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