An SMA-actuated soft robot with encircling gripping by adjustable grasping span

Shape Memory Alloy (SMA) actuators are used in the soft robots, which were used to crawl objects with fragile surfaces due to the flexibility and small volume of the SMA. However, the actuator is disadvantaged in providing output force due to the SMA material’s own property, like high power-to-weight ratio. In this article, a novel SMA-driven soft gripper structure is designed and validated, which realizes the adjustment of the initial angle of the actuator and the positioning distance through an adjustment mechanism. The gripper encircles gripping with a 100/% success rate achieved for (20–70 mm) objects, with a maximum gripping span of 150 mm. In addition, combined with the FEM (finite element method) to capture the best parameters for the device, many design details are considered, like the drive model and the gripper structure. Finally, a validation test for the device to achieve a 100/% success rate in grasping targets in the shape of a sphere and cone, and grasp a maximum of 670 g of a bottle of water. The results show that the gripper can reliably grasp the object, and has the potential to grab uneven and fragile objects by adjusting the mechanism.