Abstract
Variable stiffness actuators (VSAs) can effectively protect humans in case of an accidental collision owing to the adjustable compliance. This paper proposes a variable radius approach to develop a variable stiffness actuator with a large stiffness range based on the antagonism principle. Unlike traditional antagonistic VSAs, the stiffness control and position control are decoupled, and stiffness adjustment is achieved through the simultaneous regulation of spring stiffness and joint radius. Specifically, the regulation of joint radius is achieved by using a variable configuration mechanism (VCM). A quadratic spring is constructed using a variable radius pulley (VRP). A novel profile function of the VRP is proposed, and mathematical models of joint stiffness are established. A VSA prototype is developed to evaluate the performance, and an experiment is carried out to verify the effectiveness of the proposed quadratic spring. Joint position and stiffness are driven by actuators with position control strategies. The results of the stiffness experiment show that the stiffness can be effectively adjusted in a large range by adjusting the joint radius and the stiffness of the quadratic spring.
Published Version
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