Simple belt gripper picks fruit carefully
Sensitive grippers are needed to harvest fruit and vegetables without causing damage. Such a gripper does not have to be elaborately designed, researchers show.
The GRIP-Tape harvests fruit with its two fingers from rotating tapes.
(Image: David Baillot / University of California San Diego)
A team of engineers at the University of California San Diego (UC San Diego) has developed a gripper called GRIP-Tape (Grasping and Rolling In-Plane – GRIP), which can also grip and rotate delicate objects using two rotating tapes. The gripper can be used in a harvesting robot, for example, to harvest soft fruit. However, it is also suitable for screwing in screws with a screwdriver, for example.
Harvesting fruit and vegetables with a robot is no trivial matter. While recognizing the position of the fruit on the tree or bush is still quite simple, it can be difficult to harvest the fruit or vegetables in such a way that they are not damaged. The necessary grippers have to proceed with care and are correspondingly complex in design.
Researchers at UC San Diego have been thinking about how they can design a gripper that can act carefully, is easy to construct and control and at the same time costs little. The result is a gripper that uses two fingers made of rotating tapes, as the scientists write in the study "Grasping and rolling in-plane manipulation using deployable tape spring appendages", which has been published in Science Advances.
Rotating tapes as fingers
The advantage of using a rotating tape for a gripper is obvious: the tapes, which are guided by deflection rollers, are made of very thin steel tape covered in soft material, are flexible and therefore adapt easily to the objects to be gripped. Nevertheless, they are stiff enough to be able to grip firmly enough. Complex sensor technology is not required to check the grip strength. The scientists state that the material is as soft as silicone, which is used in soft robots. Accordingly, the risk of injury to humans is also very low.
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The straps each form a triangle and thus form a "fingertip". This is designed to be movable. A total of four motors control the finger movements independently of each other. The fingers can be extended or shortened. This allows them to reach objects that are further away in inaccessible places.
The entire length of the straps can be used as a gripping surface. What's more, the straps can rotate and thus turn gripped objects. As the researchers have demonstrated in field trials, the rotating movement makes it easier to remove fruit from trees or bushes.
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According to the scientists, the GRIP-Tape has a wide range of applications. For example, they were able to use it to screw in screws and light bulbs.
The researchers at UC San Diego now want to further improve the gripper and equip it with more sensors and artificial intelligence. This should give it autonomous capabilities so that it can carry out harvesting work independently, for example.
(olb)
