In order to solve the limitation of traditional rigid robot application in specific fields, a composite flexible joint with active and passive variable stiffness characteristics is designed. By studying the structure of variable stiffness flexible joints at home and abroad, the variable stiffness flexible joint is divided into two kinds of lever mechanism and cam mechanism according to the structure principle. And based on the principle of cam mechanism, the integration of Active-Passive variable stiffness in the same joint is realized by the compact design. The curve of cam groove is optimized through establishing mathematical model, and the property that the equivalent stiffness of joints increases gradually with the flexible deformation is finally realized. On this basis, the stiffness characteristics of flexible joints are analyzed. The static and dynamic stiffness measurement experiments of the joint prototype were carried out and the experimental results show that the variable stiffness flexible joint can realize the active and passive stiffness adjustment function and adapt to the existing robot mechanism in structural design.
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