Design and analysis of a novel hybrid-driven continuum robot with variable stiffness

Abstract

• Hybrid-driven variable stiffness continuum robot with dual-plane constraint design. • Independent robot stiffness regulation and endpoint positioning. • Stiffness independent of PMA radius, making design extensible to multiple sections. • Static model for describing the robot's behavior. Compliance and lower inertia are two essential features for safe physical human-robot interaction (pHRI). Continuum robots exhibit great potential for such situations due to their intrinsic compliance and lightweight links. However, there is a trade-off between compliance and positioning accuracy, of which variable stiffness is a potential method to address this conflict. This paper presents a novel hybrid-driven continuum robot with a dual-plane backbone structure, in which the stiffness regulation is independent from the positioning. Through the dual-plane constraint, the robot's stiffness is made independent of the pneumatic muscle actuations’ (PMAs) radius, making the design easily extensible to multiple sections. Then, a static model based on virtual work is further constructed to characterize the robot's behavior. Experiments and simulations show that the proposed stiffness regulation mechanism has stiffness range of over 278%, and the ratio of positioning error at the endpoint of continuum robot to the total robot length is 2.54%. The modeling simplicity and the decoupling between positioning and stiffness regulation provide a solution for the conflict between positioning accuracy and safety.