Multimodal steerable earthworm-inspired soft robot based on vacuum and positive pressure powered pneumatic actuators

This article presents a multimodal steerable earthworm-inspired soft robot based on vacuum and positive pressure powered pneumatic actuators capable of crawling both inside pipelines and on planar surfaces. The optimized modular vacuum pressure-driven actuator can generate deformation and anchoring motion through a unified structure under low vacuum pressure, giving it significant speed advantages and multi-modal locomotion capabilities. Meanwhile, the positive pressure powered actuator (PPPA) enables the robot to achieve controlled multi-directional and multi-degrees-of-freedom steering, moreover, enhances the consistency of the driving mechanism. The incorporation of front-end pressure sensing enables the robot to autonomously detect and evaluate pressure, facilitating automatic obstacle avoidance through the activation of corresponding turning units of PPPA. In the process of optimizing motion parameters, the overall motion efficiency has been improved by 16.7% by improving the control law. Through adjustments and optimizations of the interval time (cycle time), the robot is able to achieve a speed of 7.16 mm s^-1during planar locomotion and 1.94 mm s^-1during in-pipe locomotion. Using the developed robot, we conducted a series of turning experiments, including surface obstacle avoidance and cross-plane crawling, which demonstrated its enhanced capability in cross-plane steering and locomotion. Its related speed indicators showcase superior overall performance compared to other developed robots of the same type.