Engineers are developing flexible grippers for drones inspired by climbing plants

HANGZHOU — A team of Chinese engineers has developed a new class of biomimetic soft grippers for drones that enable unmanned aerial vehicles (UAVs) to perform various tasks, such as retrieving a key hanging from a tree branch or plucking branches in moving water.

Air transport and manipulation expands the capabilities of drones, but the rigid grippers they use tend to be heavy, have a single gripping mode, and are limited in the shape and size of the object that can be gripped .

Tendril plants are often characterized as having exceptional grappling hooks, possessing the remarkable ability to cling tightly to branches with their tangled, soft, gripping forms. There is also another category of climbing plants that have evolved hook-like structures that allow them to scale the vertical surfaces of tall buildings.

Researchers at Zhejiang University took inspiration from these vines and designed two U-shaped eccentric circular tube actuators. The U-shaped bending capability of these actuators allows drones to grasp objects with their hands. using a hook or a vine-shaped rope.

Based on these two types of actuators, the researchers then constructed two types of flexible clamps, thus forming autonomous systems that can be directly controlled by voltage.

The soft-tendril climber-inspired gripper is designed for delicate gripping, while the hook-climber-inspired gripper can be used for tasks requiring strong gripping, according to a study published as the cover story in the latest edition of the journal Science Advances.

The load capacity of a single actuator with hook structures is about 29% higher than that of an actuator without such a hook, and it can support a maximum weight of about 450 grams, according to the study.

This type of drone-mounted gripper has demonstrated its capabilities by successfully grabbing common household objects like plastic bottles, glass beakers, tongs and ceramic ornaments.

In an outdoor experiment, a drone flew toward a key hanging from a tree branch. Its self-adapting gripper passed through tree branches and then managed to firmly grip the key via tension applied to the resistance wires.

This UAV gripping solution can be useful in environmental protection, where it can be deployed for tasks such as collecting waste from nature and removing waste from rivers and lakes. In freshwater ecosystems, manual collection currently remains the primary method of cleaning up waste, meaning it is labor intensive.

In another outdoor experiment, the research team used a drone to retrieve a branch suspended in a lake. A drone flew to a specific area of ​​the lake and submerged the pincer in the lake. The elongated U-shaped gripper then demonstrated its effectiveness by successfully snagging the branch, while its self-contained system steadily supplied gas underwater, providing a secure and firm grip on the object. Eventually, the drone ascended and returned to shore.

Unlike rigid grippers, the soft, adaptable gripper can absorb vibrations transmitted by drones and also allows an object to rotate or move within the gripper.

Outdoor applications have highlighted the unique benefits of soft grippers in a wide range of harsh environments. Such grippers can work effectively even in cases of low positioning accuracy, reducing the need for complex planning regarding grasp execution, according to the researchers.

The researchers added that the soft grippers have proven that they can be used for efficient transportation of UAVs by winding or hanging objects with manual assistance on difficult transportation terrains, such as steep mountain slopes.