Bioinspired Multimodal Terrestrial Locomotion of a Soft Quadrupedal Millirobot Driven by Magnetic Torque

The ability to achieve controllable multimodal locomotion on complex terrains is crucial for the practical applications of small-scale legged robots. In this study, a novel magnetically actuated soft quadrupedal terrestrial millirobot was designed. Inspired by biological terrestrial locomotion modes, three distinct locomotion modes-quadrupedal bounding, quadrupedal pacing, and bipedal walking-were realized through a combination of various postures under a uniform external magnetic field and asymmetrical friction effects induced by magnetic torque. The characteristics of these modes were examined and compared, including the effects of magnetic field strength, swing angle, and surface roughness on stride length. Furthermore, the line-of-sight control method was implemented in path-tracking experiments, enabling closed-loop control on complex paths and improving tracking accuracy. This research holds significant potential for applying magnetically controlled small-scale robots in the bioengineering and industrial micromanipulation fields.