Smooth and inclined surface locomotion and obstacle scaling of a C-legged miniature modular robot

Abstract

This work investigates the locomotion of a modular C-legged miniature robot with soft or rigid backbones on smooth, rough, and inclined terrain. SMoLBot-C is a C-legged miniature robot with soft or rigid backbones and foldable modules. The robot's climbing capabilities with soft and rigid C-legs and different backbones on rough terrain with obstacles and the robot's mobility on an inclined surface are compared. Our results show that the C-legged robot with soft legs and soft backbones can climb up to a higher obstacle, and walk on surfaces with higher inclination angles compared to the same robot with rigid legs and backbones, regardless of the number of modules (legs). Additionally, a velocity comparison study using SMoLBot-C operating at two different gaits is conducted. The results show that the robot with soft legs and compliant-I backbones operating with trot gait possesses the highest velocity compared to the other robots with similar leg numbers. Moreover, the effect of a compliant tail on the robot's locomotion on smooth and rough terrains is investigated, where the results show that the robot with the compliant tail is capable of walking on surfaces with higher inclination angles compared to the same robot without a tail. Furthermore, adding a tail to the two-legged SMoLBot-C doubles the maximum scalable obstacle height; the robot with a tail can climb up an obstacle 2 times higher than a module's height. Locomotion analysis in this manuscript provides a better insight into C-legged miniature robots' locomotion with soft or rigid legs while the modular connections' structural stiffness varies from rigid to soft.