Vacuum-Driven Class-2 Tensegrity-Based Mechanism for Quadrupedal Robot Motion

Tensegrity structures are an assembly of rigid struts in compression with elastic members in tension that are in equilibrium. The motion of tensegrity-based robots can be dynamically achieved by actively adjusting this equilibrium and has been used mainly to produce rolling robots. However, these tensegrity robotic structures generally lack the stiffness required to sustain large payloads. This letter explores the integration of a class-2 tensegrity structure in tandem with vacuum-based pneumatic artificial muscles (PAMs) to create a versatile mechanism capable of achieving planar motions. The objective is to emulate the walking pattern of a quadruped robot while generating substantial forces throughout its motion. The study encompasses the design and fabrication of the tensegrity structure, followed by a comprehensive evaluation of its range of motion, force production, and torque. The successful implementation of this structure into a quadrupedal robot is detailed, showcasing its ability to facilitate forward and backward locomotion, negotiate upslopes, and endure payloads of up to 10 kg. This research underscores the effectiveness of higher class tensegrity structures in efficiently transmitting forces from contractile PAMs, resulting in mechanisms with robust mechanical capabilities and expansive ranges of motion.