Stanford "manipulator" into fine! Take eggs gracefully and play basketball bravely, published in the sub Journal of science
2021-12-17
On Wednesday, a new achievement of Stanford engineers was published in science robotics, a subsidiary of science, the top international academic journal. Inspired by gecko toe grasping, researchers have developed a manipulator "farmhand" with both dexterous and stable grasping ability, which can stably grasp eggs, grapes, basketball and other objects. Unlike many of our common manipulators, the multi finger joint of this manipulator can be expanded and retracted in a wider range like a human hand. As shown in the figure below, it can grasp eggs, basketball and even objects larger than itself in a way similar to "picking". ▲ grab eggs Some manipulators can grasp eggs skillfully, and some can grasp basketball smoothly, but unlike hands, few manipulators have these two skills at the same time. Wilson Ruotolo, 21, a former graduate student in the bionics and dexterous manipulation Laboratory of Stanford University, said: "you will see the manipulator grasp strongly and accurately, and then suggest that they can do anything. What we want to solve is how to create a dexterous and powerful manipulator." A paper on the manipulator by postgraduates Rotolo and Dane Brouwer of the bionics and dexterous manipulation Laboratory of Stanford University was published in the journal Science robotics on December 15. Link: https://www.science.org/doi/10.1126/scirobotics.abi9773 1、 The original intention is to help farmers. It's nothing to pick fruit and hold basketball The researchers combine the adhesive made based on the gecko toe grasping principle with the customized manipulator, aiming to create a manipulator that can be grasped with subtle force, which can realize large-scale expansion and retraction similar to the human hand. The original intention of the researchers is to use the manipulator to gently operate the fruit as a robot agricultural auxiliary tool. As a general manipulator that can efficiently use dry bonding technology, it maintains the softness and dexterity of picking eggs from cartons and grapes from grapevines. ▲ grab grapes It can open the "palm" greatly and manipulate larger objects, such as basketball, can drinks and so on. ▲ grab the basketball This manipulator can also control heavy objects many times larger than itself. ▲ handling large objects In addition, the manipulator can grasp two objects at the same time. ▲ grab two objects at the same time "The first application of gecko adhesive is related to climbing robots, climbers or very large and smooth objects in grasping space. However, we have been considering using them for more practical applications." "But it turns out that gecko adhesives are actually very picky," Cutkosky said The first use of gecko adhesive on a multi fingered humanoid manipulator is a challenge, which requires special attention to the tendon controlling the manipulator's fingers and the design of the finger pad under the adhesive. 2、 Use intermolecular forces for a firm grip One advantage of the parallel manipulator over the more humanized multi fingered manipulator is its high grip potential, so it can use a single precise finger to obtain power, while the multi fingered manipulator farmhand uses gecko adhesive to provide more grip ability. The manipulator benefits from two biological inspirations. The first is the human hand, which has multi jointed fingers, but only four fingers, and the second is the gecko. Based on the inspiration of gecko toe grasping, one of the authors of the paper Under the leadership of mark Cutkosky, Professor Fletcher Jones of Stanford University School of engineering, the research team developed a gecko adhesive with strong grip but non stick, which was applied to the fingers of the manipulator. ▲ schematic diagram of manipulator Like gecko toes, a robot hand coated with Gecko adhesive can be fixed to an object through a tiny flap. When in full contact with the surface, these flaps produce van der Waals force (intermolecular interaction force), which is caused by subtle differences in the position of electrons outside the molecules. Therefore, the adhesive only needs very little force to firmly grasp the object. Another advantage of this adhesive is that they do not stick or leave residue when they feel. After applying gecko adhesive, the manipulator needs to rely on the front of the finger rather than the tip to grasp the object, which can provide more usable contact area. In order to explore the trade-off, the researchers increased the torque of the manipulator brake by eliminating the constraint of fixed final link length. 3、 Increase the rib structure and expand the gripping area The key to the problem is that gecko adhesive must contact the object surface in a specific way to activate van der Waals force. When gecko adhesive is applied to a relatively flat surface, the way of contact with objects can be easily controlled. However, when it is necessary to rely on multiple fingers with Gecko adhesive to grasp the object and contact the object at different angles, that is, using farmhand to grasp, the control of gecko adhesive is more difficult. In order to solve this problem, the researchers added a layer of finger pad under the adhesive. The paper pad is made of a foldable frame like structure and can be bent with little force. Regardless of the position or angle of contact, the ribs are bent to ensure equal force on the adhesive pad and prevent any premature sliding from causing the object to fall. ▲ finger pad design of manipulator "If you move these ribs, no matter where you start, the ribs will produce a similar force." "It's a simple physical behavior that can even be deployed outside of robotics, such as uppers or all terrain tires," browell said The tendon of the human hand is very important, which can realize large-scale expansion and retraction. However, many manipulators and clips are designed in a "C" shape, just like picking up things with only the fingertips. However, this manipulator is based on the tendon principle of the human hand to achieve a larger gripping area. A pad is installed at the end of the finger, which also provides more surface area for gecko adhesive. Another problem of designing flexible and powerful manipulator is that the existing computer simulation is difficult to predict the real performance of soft objects, so it is particularly difficult to make the design appropriate. However, researchers have benefited greatly from 3D printing and testing many hard and soft plastic components, which has also accelerated their research process. They even said, "if it had been five years ago, this study would not have been successful, or at least much slower." Further improvements to the manipulator may appear in the form of feedback function, which will help users understand its grasping mode and how to grasp better when using the manipulator. Conclusion: it is flexible and steady to promote commercialization Multi finger manipulator is more flexible than parallel manipulator, but it also needs to have the robust function of parallel manipulator if it wants to be used in real life. Stanford researchers combine the flexibility and stiffness of the manipulator, which can grasp eggs, watermelons and other objects larger than themselves. Secondly, the prototype of the first generation manipulator farmhand is low-cost, which also provides conditions for its upgrading. Researchers said that in the future, higher performance motor torque will achieve higher tendon tension, and the use of harder ribs can also improve the overall stability of the manipulator. Researchers are also considering further commercialization of the manipulator. (Xinhua News Agency)
Edit：Li Ling Responsible editor：Chen Jie
Source：zhidxcom
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