Design and Modeling of Large Helical Deformation Composite Actuators Under Complicated Loading Conditions

Soft helical actuators, characterized by high compliance, flexibility, and dexterity in the 3-D space, are particularly promising candidates in complex and unstructured applications. However, there are few researches on the large deformation of the helical actuators, and the existing modeling methods for helical actuators are based on the constant curvature (CC) assumption and only the load applied to the end of the actuator is considered. When the helical actuators are subjected to complicated environmental loads, the CC model can no longer describe its actual morphology and deformation. In this article, a class of laminated composite actuators made up of four different layer materials are proposed, whose multiple kinds of helical deformation can be tailored by changing orientated direction and volume fraction of the fibers of the fiber reinforcement layer. Based on the piecewise CC (PCC) model and the minimum potential energy (MPE) method, we propose a segmented modeling method for the large deformation of the helical actuator under external loads. The geometric and mechanical models are established to characterize the large deformation of the proposed helical actuator under input pressure and external loads. Finally, both finite element (FE) analysis and experiments are conducted to verify the validation of the theoretical model, which reveals a consistency between the predicted deformation of the helical actuators and the experimental results.