Abstract A multi-degree-of-freedom (multi-DOF) waist mechanism is required for robotic rats to perform species-typical behaviors, but the existing waist mechanisms are heavy and cumbersome. To solve this problem, we propose a linkage-based slider-coupled symmetric swing (S3) mechanism, which features a single-input multiple-output structure, allowing it to couple multiple DOFs. The linkage mechanism has a variety of forms and linkage curves, making the S3 mechanism suitable for multiple-constraint optimization. Based on kinematic and dynamic analyses, we constrain the S3 mechanism in terms of bending angle, transmission angle, symmetry, and its existence, and then we optimize its dimensions using an interior-point method to make it compact. Compared with an existing waist mechanism, the proposed waist mechanism has only 47.8% of the weight and smaller dimensions, making it more lightweight and compact. Experiments on a robotic rat show that the proposed waist mechanism enables a robotic rat to perform rat-like upright rearing in 0.5s and tail grooming behavior in 0.4s, indicating its good biomimetic and dynamic performances. Comparisons between two generation robotic rats also reveal that the robot with new waist mechanism has similar (sometimes superior) pitching and bending abilities with the former one.

中文翻译：

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一种轻巧紧凑的机器鼠腰部机构设计与优化

摘要 机器鼠执行物种典型行为需要多自由度（multi-DOF）腰部机构，但现有的腰部机构笨重笨重。为了解决这个问题，我们提出了一种基于连杆的滑块耦合对称摆动 (S3) 机构，该机构具有单输入多输出结构，可以耦合多个自由度。联动机构具有多种形式和联动曲线，使得S3机构适用于多约束优化。在运动学和动力学分析的基础上，我们从弯曲角、传输角、对称性及其存在性方面约束了 S3 机构，然后我们使用内点法优化了其尺寸，使其紧凑。与现有的腰部机构相比，拟议的腰部机构只有47个。8% 的重量和更小的尺寸，使其更加轻便和紧凑。对机器鼠的实验表明，所提出的腰部机构使机器鼠能够在 0.5s 内完成类似老鼠的直立行为，在 0.4s 内完成尾巴梳理行为，表明其具有良好的仿生和动态性能。两代机器鼠之间的比较还表明，采用新型腰部机构的机器人与前一代机器人具有相似（有时更出色）的俯仰和弯曲能力。