MiNI-Q: A Miniature, Wire-Free Quadruped with Unbounded, Independently Actuated Leg Joints

This paper presents MiNI-Q2, a miniature, wire-free quadruped robot featuring independently actuated, mechanically unbounded 2-DOF leg joints. The motivation behind this research stems from the common limitations imposed by physical joint restrictions in legged robots, which can hinder workspace, dictate gait design, and potentially damage hardware. The study outlines the mechanical design, kinematic analysis, and experimental validation of MiNI-Q2. The innovative leg design facilitates various locomotion styles, including oscillatory gaits and rotary movement, while allowing for compact folding to a height of just 2.5 cm. Experimental results indicate that MiNI-Q reaches speeds of up to 0.46 m/s and exhibits versatile locomotion capabilities such as low-clearance crawling, stair climbing, and jumping. The engineered wire-free architecture enhances assembly reliability, particularly at small scales, building upon advancements from prior designs. Notably, all mechanical and electrical design files have been made available as open source to promote reproducibility and foster further research in the field.