Zeng Yangbin, Hu Qiao, Sun Liangjie, Jiang Chuan, Zhang Tangjia, Li Shijie, Shi Xindong
School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, P. R. China.
Shaanxi Key Laboratory of Intelligent Robots, Xi'an Jiaotong University, Xi'an, P. R. China.
Soft Robot. 2025 Apr;12(2):253-267. doi: 10.1089/soro.2023.0260. Epub 2024 Oct 3.
The unique rigid-flex connection between the fin-rays and fin-surface in a bionic undulatory fin robot endows the fin-surface with both active flexibility and load-bearing capacity, enabling this robot to perform amphibious motions in underwater, terrestrial, and even marshy environments. However, investigations into dynamic modeling problems for the undulatory fin robot, considering the impact of nonlinear deformation and frictional contact on ground locomotion performance, are scarce. Given this, based on the absolute nodal coordinate formulation (ANCF), this paper presents an efficient and accurate nonlinear dynamic model for this robot to elucidate the fin's flexible deformation and motion law. This model considers material, geometric, and boundary nonlinearities, utilizing ANCF thin plate elements and reference nodes to individually describe the fin-surface and fin-rays of the undulatory fin. Then, by using the master-slave technique, a frictional contact formulation for the fin and the ground is proposed. Furthermore, we conduct in-depth research and analysis on the formation and undulatory motion of the undulatory fin, encompassing its static deformation, static contact deformation, and frictional contact motion, and successfully obtain its responses under various conditions. Research indicates that during fin-surface motion, longitudinal sliding or a tendency for sliding at the contact points results in the undulatory fin moving in a crawling gait. The proposed theoretical model correctly captures the fin's complex nonlinear deformations and frictional characteristics and reveals its ground locomotion mechanism, whose effectiveness and superiority are validated through numerical examples and experiments.
在仿生波动鳍机器人中，鳍条与鳍面之间独特的刚柔连接赋予了鳍面主动灵活性和承载能力，使该机器人能够在水下、陆地甚至沼泽环境中进行两栖运动。然而，考虑到非线性变形和摩擦接触对地面运动性能的影响，对波动鳍机器人动力学建模问题的研究却很少。鉴于此，本文基于绝对节点坐标公式（ANCF），提出了一种高效、准确的该机器人非线性动力学模型，以阐明鳍的柔性变形和运动规律。该模型考虑了材料、几何和边界非线性，利用ANCF薄板单元和参考节点分别描述波动鳍的鳍面和鳍条。然后，通过主从技术，提出了鳍与地面的摩擦接触公式。此外，我们对波动鳍的形成和波动运动进行了深入研究和分析，包括其静态变形、静态接触变形和摩擦接触运动，并成功获得了其在各种条件下的响应。研究表明，在鳍面运动过程中，接触点处的纵向滑动或滑动趋势导致波动鳍以爬行步态运动。所提出的理论模型正确地捕捉了鳍的复杂非线性变形和摩擦特性，揭示了其地面运动机制，通过数值算例和实验验证了其有效性和优越性。
