Abstract: Limbless creatures such as snakes and worms can effectively move in various environments such as narrow spaces, ruins, rugged terrain, soft or muddy ground, and so on, becoming the imitation targets for biomimetic robots. However, existing worm-like robots mainly move in pipes or on a hard plane, and their adaptability to environments is still limited. This paper presents a new design and prototype of a worm-like robot that can crawl in various environments. The robot consists of a soft skin and a metameric skeleton. The skin has biomimetic setae that assist in movement, and integrates ripple and folding structures to achieve tight wrapping of the skeleton and low resistance adaptation to the large deformation of robot peristalsis. The skeleton is constructed based on a novel telescopic module that mimics the deformations of the earthworm segments through a space symmetric parallel coupled gear linkage mechanism. A kinematic analysis of the telescopic module provides the quantitative relationship between the input torque and output forces of the telescopic module to ensure necessary output forces for the robot crawling. Three gait modes of a prototype robot with four telescopic modules are introduced based on the concept of anchoring segments. A kinematic analysis method for the worm robot under different gait modes is provided. The slip rate to evaluate the efficiency of robot crawling has been defined. Experimental results indicate that the prototype robot can crawl more efficiently with more anchoring segments in various environments such as pipes, sand, water, and so on.

Key words: Bio-inspired robot')">Bio-inspired robot, Spatial mechanism, Large deformation skin, Kinematic model, Peristaltic locomotion