Origami-inspired Variable Stiffness actuator for Safe Human-Robot Interaction

Safety is the most important factor in collaborative robots. With the application of collaborative robots in increasingly complex scenarios, the reliability of collaborative robots faces serious challenges when performing complex actions. Variable stiffness drives are widely valued for their adequate safety. In this paper, an origami-inspired variable stiffness actuator (OVSA) is proposed, which draws on the principle of origami and uses torsion springs and hinge fixed points to form a variable polygon structure as a special elastic component. It has a lightweight and compact structure and can theoretically achieve stiffness range from zero to infinity. The use of Archimedean Spiral Cam (ASC) as the transmission element for stiffness transformation further increases the compactness of the structure, while maintaining stiffness with very little torque, improving energy efficiency. The stiffness equation of OVSA is verified by experiments, and the results show that its stiffness is high when the deflection angle is close to zero degrees and decreases rapidly with the increase of deflection angle, which makes it have sufficient safety and energy storage capacity.