Abstract: Lizards use the synergy between their feet and tail to climb on slopes and vertical terrains. They use their soft adhesive feet with millions of small hairs to increase their contact area with the terrain surface and press their tails against the terrain to actively maintain stability during climbing. Inspired by this, we propose a bio-inspired climbing robot based on a new approach wherein the synergy between soft feet and an active tail with a soft adhesive tip allows the robot to climb stably on even and uneven terrains at diferent slope angles. We evaluate and compare the climbing performance of the robot on three diferent terrains (hard, soft, and fufy) at diferent slope angles. Various robot confgurations are employed, including those with standard hard feet and soft feet in combination with an active tail—with and without a soft tip. The experimental results show that the robot having soft feet and a tail with the soft tip achieves the best climbing performance on all terrains, with maximum climbing slopes of 40?, 45?, and 50? on fufy, soft, and hard terrains, respectively. Its payload capacity depends on the type of terrain and the inclination angle. Moreover, our robot performs multi-terrain transitions (climbing from horizontal to sloped terrains) on three diferent terrains of a slope. This approach can allow a climbing robot to walk and climb on diferent terrains, extending the operational range of the robot to areas with complex terrains and slopes, e.g., in inspection, exploration, and construction.

Key words: Bio-inspired climbing robots , · Climbing robots , · Soft foot , · Active tail , · Soft terrain , · Terrain transitions