An origami-inspired robotic fingertip with shape-morphing capabilities

An example grasp employing a pair of designed morphing fingertips. Credit: Kan et al.

To perform tasks that involve moving or handling objects, robots should swiftly adapt their grasp and manipulation strategies supported the properties of those objects and therefore the environment surrounding them. Most robotic hands developed to date, however, have a hard and fast and limiting structure; thus, they'll perform a limited number of movements and may only grasp specific forms of objects.

Researchers at city University of Science and Technology have recently developed a robotic fingertip which will change its shape and switch across three different configurations, which could allow it to know a broader style of objects. This fingertip's unique design, outlined in a very paper presented at this year's IEEE International Conference on Automation Science and Engineering (CASE), is inspired by origami, the renowned Japanese art of paper folding.

"Our study was inspired by two common observations in current research and industrial applications," Zicheng Kan and Yazhan Zhang, two of the researchers who administered the study, told TechXplore via email. "The first relates to parallel grippers developed in past research studies, which could help to attain industrial automation. These grippers require well-selected grasping points, otherwise static equilibrium won't be achieved."

Researchers are trying to develop techniques to manage the grasping poses of robotic grippers for several decades. However, most existing approaches have significant limitations that prevent them from generalizing well across different objects. the primary objective of the study dole out by Kan, Zhang and their colleagues was to develop a fingertip which will be easily controlled which can perform a range of poses.

"The other past observation that inspired our study is that for a stable grasp, engineers need to design a selected clamper fixed on parallel gripper for manipulations, e.g. pick and place, etc.," Kan and Zhang said. "It is tedious when an item on the mechanical system is modified with a special shape, which ends up in an inefficient manual replacement of the clampers. The morphing fingertip we created could help to mitigate or overcome this issue."

The robotic fingertip design created by Kan, Zhang and their colleagues relies on other robotic structures presented in their previous studies. In 2019, for example, the researchers created an origami-inspired monolithic soft gripper with a flat fingertip. While this gripper can even deform and alter shape, its performance in terms of payload and dexterity is poor, thanks to the flatness and softness of the fingertips.

"A Ph.D. student in our group, Mr. Song Haoran, also previously published a paper on contact surface clustering, showing three typical contact primitives for the representations of major local geometries," Kan and Zhang said. "These fingertips mounted on parallel grippers were tested on different objects, indicating feasibility and stability of the grasps. This paper inspired us to style a morphing fingertip, with its morphology configurations within the three contact primitives."

The new origami-based shape morphing fingertip developed by Kan, Zhang and their colleagues at city University of Science and Technology has two main components: a soft origami skeleton that acts because the fingertip's morphing surface and motor-driven four-bar linkages that function actuation and transmission mechanisms.

Contact primitives of the fingertip in three morphing modes. Credit: Kan et al.

The researchers placed a ball joint at the middle of the fingertip to enable three-dimensional free rotation and support of the highest surface. additionally, they used servo motors (i.e., a category of rotary actuators) to independently control four leaf facets placed on the soft origami skeleton.

"With the combinations of various poses on each leaf facet, many configurations are often achieved for distinct grasping modes, e.g., convex mode, concave mode and tilted planar mode," Kan and Zhang explained. "These modes are often simulated and predicted by our kinematic model."

The researchers evaluated the three morphing modes that their fingertip can do on movements that are essential for effective robotic grasping. as an example, they tested the effectiveness of the convex mode for what's called pivoting and pinch grasping, the concave mode for performing an influence grasp and also the tilted planar mode for in-hand manipulation and reorientation.

Overall, they found that the fingertip they developed has many advantageous characteristics, including the flexibility to shift quickly between different morphing primitives and grasping modes, furthermore as between stable and dexterous grasp modes supported the task at hand. The fingertip's configuration is efficiently simulated and guided by the kinematic model they used.

Trajectory tracking within the configuration space. Credit: Kan et al.

"We introduced a replacement solution to the need of adaptation and dexterity of robotic grasping that would be applied both in academic and industrial settings, without adding significant extra costs," Kan and Zhang explained. "Our design can inform future works that try and address these problems using compact, controllable and morphing fingertips."

In the future, the shape-morphing fingertip designed by Kan, Zhang and their colleagues may be integrated on variety of existing and newly developed humanoid robots. because it is comparatively low-cost (i.e., it costs approximately U.S. $5 to make, excluding the control board), it could help to automate production line processes, reducing the prices related to continuously changing the form of products supported what existing grippers can manipulate.

While the fingertip created by this team of researchers achieved highly promising results, there are still variety of issues to deal with and tests to run before it may be commercialized. as an example, there's currently a discrepancy between its actual performance and also the predictions made by the kinematic model, which Kan, Zhang and his colleagues decide to tackle in their future works by slightly altering its design and fabrication process.

"Another area that we decide to target in our future studies is miniaturization, employing a smaller motor and more compact structure in order that the fingertip is easily integrated on robot hands," Kan and Zhang said. "In addition, currently, the structure operates with an open-loop control strategy on morphing. Sensing plays a vital role for a strong end-effector in practical applications, so we'll also attempt to add this capability within the future."

More information: Origami-based shape morphing fingertip to enhance grasping stability and dexterity. arXiv:2010.04931 [cs.RO].

An origami-inspired monolithic soft gripper based on geometric design method. 2019 2nd IEEE International Conference on Soft Robotics (RoboSoft)(2019). DOI: 10.1109/ROBOSOFT.2019.8722746.

Fingertip surface optimization for robust grasping on contact primitives. IEEE Robotics and Automation Letters(2018). DOI: 10.1109/LRA.2018.2789842.

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