Vine-Like, Power Soft Gripper Based on Euler's Belt Theory

Abstract

Soft robots hold the potential for use in disaster sites where it is difficult to predict the external environment and the manipulation of irregularly shaped heavy objects is required. However, existing soft robots possess the low load capacity. Therefore, we propose a vine-like, power soft gripper that grasps an object by wrapping it, and we fabricated a prototype. The gripper is based on Euler's belt theory, the load capacity increases with the wrap angle and it is demonstrated by load capacity measurements. A grasping experiment demonstrated that the gripper could grasp objects of various shapes. This gripper wraps around an object using the restoring force exerted by the constant-force spring. Hence, the gripper cannot lift heavy objects that tend to rotate during lifting. However, it was confirmed that a twin-gripper with opposite helical directions could grasp such objects. It was also confirmed that twin-gripper could grasp an object weighing 1660 N although its two constant-force springs possess a small load of 43 N. This indicates that the grasping load force surpassed that generated by the spring coiling force. Finally, the gripper was attached to a construction machine robot, and a pick-and-place demonstration was conducted.