The Caterpillar Robot demonstrates a new approach to moving soft robots


Researchers at North Carolina State University have shown a caterpillar-like robot that can move forward and backward and dive into tight spaces. The crawler robot’s motion is driven by a new pattern of silver nanowires that use heat to control how the robot bends, allowing users to guide the robot back and forth.

“Local flexion of its body controls the movement of the caterpillar — its body bends differently when it pulls itself forward than when it pushes itself backward,” says Yong Zhu, author of an article on the work and Andrew Adams Professor. Full-time in Mechanical and Aerospace Engineering in North Carolina. “We were inspired by the biomechanics of the crawler to mimic this local curvature and use nanowire heaters to control similar curvature and motion in the crawling robot.

“Engineering soft robots that can move in two different directions is a big challenge in the field of soft robotics,” Zhou said. “The embedded nanowire heaters allow us to control the movement of the robot in two ways. We can control the bending sections of the robot by controlling the heating pattern of the soft robot. And we can control how much these sections bend by controlling the amount of heat applied.”

The Caterpillar Boot is made of two layers of polymer, which react differently when exposed to heat. The substrate shrinks or shrinks when exposed to heat. The top layer expands when exposed to heat. A pattern of silver nanowires is embedded in the expanding polymer layer. The model includes several key points where the researchers can apply an electric current. The researchers can control which sections of the nanowire pattern are heated by applying electric current to different contact points, and they can control the amount of heat by applying more or less current.

“We showed that a crawling robot is able to pull itself forward and push itself backward,” says Shuang Wu, first author and postdoctoral researcher at NC State. “In general, the more we applied now, the faster it moved in both directions. However, we found that there was an optimal cycle, which gave the polymer time to cool, allowing the muscle to relax before contracting again. If you try to roll the robotic crawler too fast, it won’t be The body has time to ‘relax’ before contracting again, which impedes its movement.”

The researchers also showed that a crawling robot’s motion could be controlled to the point where users could steer it under a very small area – similar to directing a robot to slide under a doorway. Essentially, the researchers can control both forward and backward motions as well as how high the robot slopes upward at any point during this process.

“This method of driving movement in a robot is very energy efficient, and we want to explore ways to make this process more efficient,” Zhou said. “Additional next steps include integrating this approach to soft robot motion with other sensors or technologies for use in different applications, such as search and rescue devices.”

The work was performed with support from the National Science Foundation, under grants 2122841, 2005374, and 2126072; and from the National Institutes of Health, under Grant No. 1R01HD108473.

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