In the construction world, certain characteristics like strength, stiffness and rigidity are highly valued for the integrity and stability of structures. In nature, however, those characteristics are rarely found – and Disney Research is taking a closer look at whether nature, as in most cases, might know better than we do.
“Rigidity is a concept foreign to the living world,” said Markus Gross, Vice President at Disney Research. “From a kangaroo’s legs to the wings of a bat, bones, tendons and cartilage are the nuts and bolts of organic machines. Our research team has developed a tool that will make it easier for us to eventually make our machines as efficient and robust as those we find in nature.”
In a new paper entitled “A Computational Design Tool for Compliant Mechanisms,” which you can access here, the researchers from the always-busy Disney Research team explain how they created a computational design tool that allows for the creation of machines that move more closely to how living things move – by bending. While flexibility might be nature’s way of designing movement, however, it’s not so easy for humans to create. We tend to create movement by linking multiple rigid objects together with hinges, but Disney Research has developed a way that makes it easier to design as nature intended.
The computational design tool is capable of taking a rigidly articulated device and automatically replacing its stiff joints with parts that achieve motion through flexibility. The tool draws from flexible mechanisms already in existence.
“Compliant mechanisms enjoy widespread use in industry – ranging from miniature actuators in microelectromechanical systems to the binder clips, backpack latches and shampoo lids common in everyday life. Even broader use in machines is attractive because of their precision and because they can be readily manufactured,” said Bernhard Thomaszewski, a former Disney scientist who is now an assistant professor at the University of Montreal.
Designing for flexibility is more difficult than designing for rigidity because it requires “a deeper understanding of how materials behave as their shape changes,” said Moritz Bächer, a research scientist at Disney Research. But the production of those pliable items is made easier through 3D printing, which can create complicated geometries in one piece using strong, flexible materials. To demonstrate the tool, the researchers 3D printed several items including the steering mechanism for a toy car, a compliant hand and a multi-jointed leg mechanism called Jansen’s Linkage.
The computational design tool replaces conventional, stiff joints with compliant mechanisms, with the only exception being hinge joints that rotate more that 360 degrees – there’s no compliant substitute for those. The tool also modifies the design to optimize the performance of the device, reducing strain that could cause breakage, eliminating collisions between components and ensuring lateral stability.
“As another limitation, we have so far focused on structurally-sound and function-preserving kinematic behavior,” the researchers state. “Dynamic effects, however, can play a role as can be observed when teleoperating with our compliant hand. These effects are, however, highly dependent on the choice of material: we sintered an individual finger of our compliant hand and observed a more high-frequent but far less pronounced dynamic behavior. An interesting direction for future work would be to extend our method to model and optimize for these dynamic effects.”
The researchers will present their work at SIGGRAPH 2017, which is taking place from July 30th to August 3rd in Los Angeles. Authors of the paper include Vittorio Megaro, Jonas Zehnder, Moritz Bächer, Stelian Coros (of Carnegie Mellon University), Markus Gross and Bernhard Thomaszewski. Discuss in the Disney Research forum at 3DPB.com.[Images: Disney Research]
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