A Lightweight and Multimotion Crawling Tensegrity Robot Driven by Twisted Artificial Muscles

Soft robots made from soft materials show great advantages over rigid robots in environmental adaptability and motion flexibility. However, too soft body makes them lose the load capacity, which limits their applications in locomotion. Although the crawling tensegrity robots with both rigid bars and flexible cables are potential to address this challenge, the existing inchworm friction drive methods are difficult to realize the motion of a single tensegrity unit. Besides, the lack of appropriate soft actuators and robot configuration also blocks the development of the crawling tensegrity robots. This article presents a new inchworm driving method realized by the inclined supporting feet. By using the twisted artificial muscle (TAM) as actuator, the combination of the TAM and the inclined supporting feet endows a single three-bar tensegrity unit with multimotion capacity and anisotropic stiffness characteristics. The designed tensegrity robot not only has high compliance but also displays high stiffness, which endows it with high load capacity. The prototype can carry a load of 150 g (7.5 times of its weight) to achieve straight and turning motions. This article provides a design idea for the crawling tensegrity robot and a theoretical foundation for improving the load capacity of high compliance robots.