Design of a torsional compliant mechanism with given discrete torque-deflection points for nonlinear stiffness elastic actuator

Abstract

Owing to inherent flexibility, compliant actuator with physical elastic elements can implement compliant interactions between robot and environment. Nonlinear stiffness elastic actuators (NSEAs) use one motor to adjust position and stiffness, which improve compactness of variable stiffness actuators, and consider high torque/force resolution and high bandwidth. The primary challenge of designing a NSEA is designing a reliable compliant mechanism with a given torque-deflection profile. In this study, a general design method of torsional compliant mechanism through given discrete torque-deflection points was proposed, where a chain algorithm based on 2R pseudo-rigid-body model was used to describe the large deformation in elastic elements. Moreover, the theoretical model of stiffness of a compliant mechanism based on series flexible beams was developed. Based on the proposed model, the dimensional parameters of proposed compliant mechanism were designed satisfying the condition of the given torque-deflection points. Finally, simulation and physical experiment of the designed compliant mechanism through three given torque-deflection points are conducted to show the effectiveness of the proposed method. The designed compliant mechanism was tested and evaluated in the self-developed NSEA.

Design and control of a compliant robotic actuator with parallel spring-damping transmission

“…Introducing physical compliance (elastic or soft materials) in robot systems plays a pivotal role in solving the interaction problem [4][5][6]. Compared with rigid ones, physically compliant actuators, for example, the series elastic actuator (SEA) [7][8][9][10], utilize elastic element as the transmission component, which provides passive compliance to the robotic systems. Even under sudden collisions, the passive filtering of the impact through the elastic element is faster and more reliable than that achieved by an active impedance control algorithm [3].…”