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This article proposes a novel soft pneumatic actuator inspired by the segmented structure of earthworms. The actuator adopts a new structure of free bottom to eliminate the constraint of the bottom and enlarge the bending capacity of the actuator. Through simulation, it is found that the new actuator improves the bending angle by 20% and output force by 40% compared with traditional actuator. Moreover, key parameters of the actuator are analyzed to acquire their effect on bending angle and bending linearity. A guideline for the design and optimization of the actuator is proposed. To validate the simulation results, we build up a test platform to test bending angle and output force of the actuators, the results shows that errors between the simulation and the test remained in the limit of about 10%. Finally, a three-jaw soft gripper is fabricated and its grasping strategy is studied. The quantitative analysis shows its excellent adaptability and load capacity.

Soft grippers can be used to grasp objects with various geometric surface structures or stiffness but typically encounter difficulty in providing high grasping force. Although the combination of soft grippers with adhesive technology can increase their load capacity, this approach has disadvantages of compatibility and limited application range. This article has reported a bioinspired design of a soft gripper that integrates flat dry adhesive, soft actuator, and microspine to improve the comprehensive grasping ability of the soft gripper on smooth or rough surfaces. The adhesive strength of flat dry adhesives with different thickness or cross-linking ratios was investigated to ensure that a large grasping force can be provided. Soft actuators with uniform and nonuniform cross-sectional heights were compared, and results indicated that the soft actuator with a nonuniform cross-sectional height exhibited remarkable advantages for designing the integrated gripper. A microspine–spring–shape memory alloy coil structure was designed to control the retraction and protrusion of microspine and distribute the load on rough surfaces evenly. The proposed integrated gripper with the aforementioned design can lift regularly or irregularly shaped objects with smooth or rough surfaces and provide a higher adhesive force than the nonadhesive gripper. After inserting a flexible pressure film sensor into the soft gripper, the surface property of the grasped object can be measured, which is beneficial for the selection of a suitable grasping strategy in unknown environments. The designed gripper can be used in many applications, such as in unmanned aerial vehicles, industrial manipulators, and climbing robots. [ABSTRACT FROM AUTHOR]

Numerous soft grippers have been developed based on smart materials, pneumatic soft actuators, and underactuated compliant structures. In this article, we present a three-dimensional (3-D) printed omni-purpose soft gripper (OPSOG) that can grasp a wide variety of objects with different weights, sizes, shapes, textures, and stiffnesses. The soft gripper has a unique design that incorporates soft fingers and a suction cup that operate either separately or simultaneously to grasp specific objects. A bundle of 3-D-printable linear soft vacuum actuators (LSOVA) that generate a linear stroke upon activation is employed to drive the tendon-driven soft fingers. The support, fingers, suction cup, and actuation unit of the gripper were printed using a low-cost and open-source fused deposition modeling 3-D printer. A single LSOVA has a blocked force of 30.35 N, a rise time of 94 ms, a bandwidth of 2.81 Hz, and a lifetime of 26 120 cycles. The blocked force and stroke of the actuators are accurately predicted using finite element and analytical models. The OPSOG can grasp at least 20 different objects. The gripper has a maximum payload-to-weight ratio of 7.06, a grip force of 31.31 N, and a tip blocked force of 3.72 N. [ABSTRACT FROM AUTHOR]