A lightweight soft gripper for envelope grasping is proposed. The main component of the gripper is a spherical latex superelastic membrane whose material properties allow a grabbing function to be realized. The grasping process includes the expansion and tightening of the membrane, and it does not require a constant supply of energy. The geometric relationship between the actuator and the target object are analyzed, from which a gripping force model is deduced to estimate the grasping ability. A test-rig was designed to verify the gripping force model experimentally. The gripper can inherently realize shape adaptability and safety. It is easy to manipulate and control for beginners. Moreover, an actuator of only 50 g can grasp and lift various objects, including fragile and irregularly shaped items with a maximum mass >650 g.
Keywords: envelope grasping; soft gripper; superelastic membrane.