Design and Grasping Force Modeling for a Soft Robotic Gripper with Multi-stem Twining

To improve the grasping power of soft robots, inspired by the scene of intertwined and interdependent vine branches safely clinging to habitats in a violent storm and the phenomenon of large grasping force after being entangled by aquatic plants, this paper proposes a soft robotic gripper with multi-stem twining. The proposed robotic gripper can realize a larger contact area of surrounding or containing object and more layers of a twining object than the current twining gripping methods. It not only retains the adaptive advantages of twining grasping but also improves the grasping force. First, based on the mechanical characteristics of the multi-stem twining of the gripper, the twining grasping model is developed. Then, the force on the fiber is deduced by using the twining theory, and the axial force of the gripper is analyzed based on the equivalent model of the rubber ring. Finally, the torsion experiments of fibers and the grasping experiments of the gripper are designed and conducted. The torsion experiment of fibers verifies the influence of a different number of fiber ropes and fiber torque on the grasping force, and the grasping experiment reflects the large load of the gripper and the high adaptability and practicability under different tasks