Researchers have developed a new robot fingertip capable of shifting shape across three unique configurations — enabling it to grasp and lift a wide spectrum of odd-shaped objects, according to a recent study outlined in a paper shared on a pre-print website and presented at the 2020 IEEE International Conference on Automation Science.
Origami-inspired robot fingertip morphs to grasp, lift oddly-shaped objects
To handle and move objects, robots need to adapt their grasp to achieve manipulation strategies using the properties of the objects and the surrounding environment, TechXplore reports.
Most robotic hands' structures limit their ability to adapt to different objects, which constrains the number of movements they can make, leaving only a few simple objects in viable reach. This is why the researchers from Hong Kong University of Science and Technology created the robotic fingertip — to solve for multiple objects using a design taking a cue from the renowned Japanese art of paper folding.
Fingertips need to strike several poses for different objects
"Our study was inspired by two common observations in current research and industrial applications," said Yazhan Zhang and Zicheng Kan, two of the researchers involved in the study, to TechXplore via email. "The first relates to parallel grippers developed in past research studies, which could help to achieve industrial automation. These grippers require well-selected grasping points, otherwise static equilibrium might not be achieved."
This comes after decades of research into developing techniques to control the poses robotic grippers must achieve to grasp different objects. Until recently, most existing designs ran into serious limitations that stopped them from effectively generalizing across varying objects and shapes.
The first goal of the study was to develop an easily-controlled robot fingertip, capable of striking many poses and performing without major issues.
Origami-based robotic fingertip has two main components
"The other past observation that inspired our study is that for a stable grasp, engineers have to design a specific clamper fixed on parallel gripper for manipulations, e.g. pick and place, etc.," said Zhang and Kan, reports TechXplore. "It is tedious when an item on the assembly line is changed with a different shape, which leads to an inefficient manual replacement of the clampers. The morphing fingertip we created could help to mitigate or overcome this issue."
The robot fingertip design is the brainchild of Zhang, Kan, and their colleagues, and also takes inspiration from structures presented in earlier studies. In 2019, the researchers built an origami-inspired monolithic soft gripper — featuring a flat fingertip.
While the gripper can deform and alter its shape, payload and dexterity performance fell short of expectations, mostly due to the softness and flatness 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," said Zhang and Kan.
"These fingertips mounted on parallel grippers were tested on different objects, indicating feasibility and stability of the grasps. This paper inspired us to design a morphing fingertip, with its morphology configurations within the three contact primitives," Kan and Zhang added.
The novel origami-based shape-morphing fingertip features two primary components: a soft origami skeleton that works like the fingertip's morphing surface, and motor-driven four-bar linkages — which work as transmission and actuation mechanisms.
Robotic finger includes servo motors for distinct grasping modes
The researchers installed a ball in the center of the fingertip to allow for free rotation in three dimensions, in addition to supporting the top surface. Moreover, they also installed servo motors (which are a class of rotary actuators) to independently control four leaf facets situated on the soft origami skeleton.
"With the combinations of different poses on each leaf facet, many configurations can be achieved for distinct grasping modes, e.g., convex mode, concave mode and tilted planar mode," explained Zhang and Kan, TechXplore reports.
Robotic fingertip needs more research before robot integration
The researchers' robot fingertip could achieve crucial movements for effective grasping, after three morphing mode evaluations. One mode involved the convex mode for what's called pivoting and pinch grasping, a second involved the concave mode for carrying out a power grasp — and a third was a tilted planar mode designed for in-hand reorientation and manipulation of objects.
In general, the research team discovered how the fingertip possesses several advantageous properties — including an ability to rapidly shift modes between different morphing "primitives" and grasping modes, including dexterous and stable grasp modes, curated for varying tasks.
More research is needed to miniaturize and optimize the robot fingertip design before the researchers can integrate it for practical use in real-life scenarios. But the scope of engineering required for one robot fingertip only goes to show how much we take for granted with our biological counterparts.