Abstract: As lunar exploration missions continue to advance, increasingly complex lunar surface environments impose higher demands on the locomotion capabilities of exploration robots. Pneumatic soft robots show distinct potential for lunar exploration owing to their good compliance, environmental adaptability, and safe interaction characteristics. However, existing pneumatic soft robots are generally limited by material flexibility and gas viscosity, resulting in slow response, low power output, and locomotion modes dominated by crawling. Although crawling enables robots to negotiate terrain such as lunar slopes and cracks, its obstacle-crossing capability remains limited. In contrast, jumping can exploit the Moon’s low-gravity environment to traverse obstacles, but is less suitable for precise exploration. To address these limitations, this study proposes a multimodal pneumatic soft robot for lunar surface locomotion that integrates both crawling and jumping capabilities. First, inspired by inchworm locomotion and the cheetah spine, an integrated rigid–flexible pneumatic actuator with monostable and bistable characteristics is developed, enabling switching between low-power and high-power output. Then, a mechanical model of the actuator is established using the pseudo-rigid-body method to characterize the nonlinear relationships among configuration, energy, and input pressure. Finally, the actuator is integrated with a unidirectional wheel-foot design to develop a prototype multimodal pneumatic soft robot for lunar surface locomotion. Experimental results show that, with an external pneumatic supply, the robot achieves a maximum crawling speed of 63.75 mm/s and can stably crawl while carrying a 1.5 kg payload, approximately 9.72 times its body mass. In the jumping mode, the maximum jump height reaches 125 mm, corresponding to an ideal lunar-equivalent height of approximately 750 mm. By switching between crawling and jumping modes, the robot can negotiate various complex terrains, including slopes, obstacles, gaps, rock steps, and confined spaces. The proposed design effectively enhances the locomotion capability of pneumatic soft robots in unstructured lunar environments and provides a feasible technical approach for future lunar exploration missions.

Key words: Lunar exploration, soft robot, multi-modal locomotion, pneumatic actuation, bio-inspired, pseudo-rigid-body method (PRBM)