A Soft and Bistable Gripper with Adjustable Energy Barrier for Fast Capture in Space

Actuators for fast capture are essential in the tasks of space structure assembly and space debris disposal. To avoid damage and rebound caused by collision, the mechanical devices for capture or docking impose very strict restrictions on the collision speed. The gripper made of soft material can realize compliant grasping, but its actuating speed and driving mode should adapt to the scenarios of grasping moving objects in space. By harnessing the rapid occurrence of structural instability and tuning its triggering conditions, we present a soft and bistable gripper for dynamic capture. The gripper deforms on the collision with other objects, and it absorbs the kinetic energy of the objects to trigger an instability, and then achieve fast grasping as well as cushioning. This process does not need any other input energy, and it greatly simplifies the conventional driving devices so as to realize the miniaturized and light-weight gripping actuation. The proper pre-deformation to the bistable structure of the gripper enables one to dynamically adjust the energy barrier for triggering the onset of instability to achieve the optimal grasping and buffering effect according to the kinetic characteristics of targets. After finishing one grasping task, the bistable gripper can automatically return to its initial state and release the target via a self-designed cable-driven mechanism. The ground-testing experiment demonstrates that the proposed soft gripper is capable to grasp, transfer, and release moving targets, and it thus possesses great potential to fulfill challenging operations in space missions.