Via analytical modeling and experimental validation, this study examines the bending stiffness adaptation of bistable origami modules based on generalized Kresling pattern.  These modules, which are the building blocks of an octopus-inspired robotic manipulator, can create a reconfigurable articulation via switching between their stable states.  In this way, the manipulator can exhibit pseudo-linkage kinematics that provides lower control requirements and improved motion accuracy compared to completely soft manipulators.  

A key to achieving this reconfigurable articulation is that the underlying Kresling modules must show a sufficient difference in bending stiffness between their stable states.  Therefore, this study aims to use both a nonlinear bar-hinge model and experimental testing to uncover the correlation between the module bending stiffness and the corresponding origami designs.  The nonlinear bar-hinge model converts the continuous Kresling origami into a pin-jointed truss-frame system so that it can approximate the Kresling module bending stiffness without incurring a high computational cost.  To ensure the accuracy of our analysis, we experimentally measure the effective torsional stiffness of paper creases and use the testing results to calibrate the bar-hinge model parameters, such as truss element stretching stiffness.  Then, we plotter-cut and assemble prototypes of Kresling origami module using thick print papers and perform three-point bending tests using 3D-printed fixtures. 

Our results show that the Kresling origami module can indeed exhibit a significant change in bending stiffness because of the reorientation of its triangular facets.  That is, at the extended stable state (1), the module bending stiffness is relatively high and dominated by in-plane facet stretching.  However, at the contracted state (0), the bending stiffness is lower and dictated by the crease folding.  By using the nonlinear bar-hinge model with experimental validation, we establish a quantitative correlation between this bending stiffness adaptation and Kresling design parameters.  A proof-of-concept Kresling module design manages to provide a bending stiffness ratio of 5.83 according to model prediction and 5.06 according to experimental testing.  Moreover, the test results from repeated loading cycles show little variation, indicating that such geomtry-induced stiffness adaption is robust for robotic applications.

The results of this study prove that the concept of reconfigurable articulation in a continuous manipulator is indeed feasible. Moreover,  they provide the necessary analytical and experimental tools for fine-tuning the generalized Kresling design according to the kinematics and other performance requirements for such robotic applications. Therefore, this study paves the way for constructing a fully-functional robotic manipulator, which will be the topic of the follow-up study.


Examine the Bending Stiffness of Generalized Kresling Modules for Robotic Manipulation

Division / Sponsors: 
Design Engineering Division and Computers & Information In Engineering Division


Paper Proceedings: https://asmedigitalcollection.asme.org/IDETC-CIE/IDETC-CIE2020/volume/83907

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