Soft Pneumatic Helical Actuators With Programmable Variable Curvatures

This letter proposes novel variable-curvature soft helical actuators (VC-SHAs) using fluidic prestressed composites (FPCs) for enhanced grasping performance. A third-order three-dimensional chained composite model called 3D-CCM is developed to pre-program variable curvatures of SHAs and predict their actuation responses. The proposed actuator design increases shape-matching areas between the objects and the soft actuators, highly improving grasping performance. Various VC-SHAs are fabricated and tested to validate the model and parametric studies are conducted to identify the effects of key parameters on actuator responses. A bioinspired passive dynamic gripper is developed with three VC-SHAs. Loading tests are conducted to evaluate its grasping success rates and maximum payload for various objects and object sizes, achieving a maximum payload of 26.56 N. The gripper is integrated to a drone to demonstrate its capability to perch on pipelines of different sizes and angles, and various objects.