Design and optimization of a passive compliant rotational joint with conjugated surface using corrugated flexure units

In designing a compliant rotational joint (CRJ) with a larger motion range, corrugated flexures (CF) were used to construct an initial curved periodic beam with greater compliance. In consideration of axis drift, the conjugated surface was adopted, and a passive CRJ was designed. Considering the indeterminate problem caused by the conjugate surface, the spatial flexibility of CRJ is modeled, and the equivalent rotation stiffness of the joint is obtained. After analyzing the stress distribution along the curved beam, the motion range was determined, and its natural frequency was derived by applying the pseudo-rigid-body (PRB) method. The rotational joint is designed and optimized with the interference and performance considered. Finally, a prototype was fabricated and tested, achieving a rotation stroke of 21.650° and a first natural frequency of 85.131 Hz, both closely matching the simulated values of 21.349° and 80.267 Hz within a 15.6 mm design domain.