A Soft Crawling Robot with Multi-Modal Locomotion Inspired by the Movement Mechanism of Snake Scales

The existing soft crawling robots usually have single-motion mode, which results in poor motion adaptability and significantly restricts the application field of the soft crawling robots. To further increase the motion adaptability of the soft crawling robots and expand their application space, in this letter, inspired by the movement mechanism of the snake scales, we present a pneumatic soft crawling robot with multi-modal locomotion based on a deployable and foldable (D-F) mechanism. The robot adopts a four-chamber bellows actuator to further enhance the robot's movement adaptability in motion space. The head and tail parts of the robot are provided with a D-F mechanism imitating snake scales, which can be opened and closed through the extension and contraction of the bellows actuator. By adopting different actuation strategies and utilizing the anisotropy of friction and the alteration of the center of gravity, the robot can achieve multi-modal locomotion such as straight walking, steering, rolling and obstacle crossing to satisfy the requirements of varied surroundings. An open-loop control system of the robot is developed to assess its motion performance. The mathematical model of the robot is established using cosserat-rod theory to clarify the relationship between actuating pressure and robot's motion variables under various motion strategy combinations. The experimental results show that the soft crawling robot designed in this study can efficiently adapt to moving surfaces with different material properties and achieve diverse motion modes under different actuation strategies. Additionally, it can adapt to exploratory tasks in unstructured environment.