A Retractable Worm Robot and Its Spatial Locomotion Control for Inspection

Retractable worm robots excel in navigating confined spaces that are inaccessible or harmful to humans, making them an innovative solution for inspection tasks in aerospace craft inspections, planetary exploration, and industrial maintenance. This article introduces RW-Robot, a novel retractable robot featuring a codesigned mechanical structure and control strategy to improve locomotion speed without sacrificing terrain adaptability. The robot utilizes a cascaded M-Canfield parallel mechanism, combining rigid stability with significant deformability for directional pointing and segment retraction. To mitigate rigidity limitations, a spatial locomotion strategy is proposed, synthesizing rectilinear gait and configuration adaptivity. First, a dual-mode bioinspired rectilinear gait integrates caterpillar-inspired cautious movement and inchworm-inspired rapid progression, enabling dynamic mode switching based on task urgency. Second, a foothold model predictive contouring control (MPCC-F) algorithm optimizes the robot’s configuration and joint solutions, effectively balancing locomotion speed and terrain compliance, particularly during sharp turns. Simulation and experimental validation demonstrate high-speed locomotion (0.34 body length per second), agile turning capabilities (radius of 0.32 body length), and slope climbing up to 75°, confirming its effectiveness for adaptive inspection tasks. Comprehensive comparisons with related worm robots highlight RW-Robot’s superior directional flexibility and rapid inspection capabilities, indicating its suitability for urgent or time-sensitive inspections in confined environments.