Servo - October 2010

Mind / Iron

by Bryan Bergeron, Editor ;

Newly Discovered Method Of Locomotion May Have Implications In Robotics

Nature has done a great job evolving creatures to move efficiently on the land, in the sea, and in the air. It’s one of the reasons biomemetics – the science of mimicking nature – is a popular basis for robotics R&D. As I’ve noted in previous editorials, one of the most fascinating and challenging areas of robotic work is in developing ‘soft’ robots.

A robot that can squeeze through a small opening and deliver aid or at least communications to someone trapped under rubble has obvious advantages over, say, a crawler that can at best only scurry on top of the rubble. Similarly, a robot that can squeeze under a door and deliver a lethal gas or other payload to the occupants has obvious appeal to the Department of Defense. However, to date, there haven’t been any clear winners in the field of soft robots. Sure, in Japan it’s common to wrap the angled metal and protrusions on robots with layers of soft foam to prevent injury to humans. And there’s at least one self-deforming wheel that can roll and jump over modest obstacles – with the caveat that power and processing are supplied externally [Hiri].

What has the soft robotics field abuzz is the publication of Visceral-Locomotory Pistoning in Crawling Caterpillars in July 2010 by scientists at Tufts University and Virginia Tech [Simon]. Based on phase-contrast xray imaging — which you can view on the web — the researchers determined that the green tobacco hornworm caterpillar pumps its internal organs as part of the propulsion process. This is a new form of propulsion that may have a direct bearing on the future of soft robotics. As of this editorial, no group has come forward with a robot that copies this rather odd form of propulsion, but I assume several labs are working feverishly on the challenge. I also don’t doubt that the patent office has a few related patents in their in-box. So, what’s there to do as a robotics enthusiast, other than wait for the academic labs to secure funding and government grants? Well, soft robotics isn’t limited to the well-to-do. You can go soft in any number of ways – from using memory wire to pneumatics. I suggest pneumatics. And you needn’t work on the microscopic scale. A foot-long caterpillar model with at least one internal bladder should do. You’ll have to study the videos posted online and then work to mimic the motion of the internal bladder of your model.

As a proof of concept, it’s usually best to keep the power and processing separate from the platform. One of the advantages of using pneumatics is the simplicity of actuators or bladders in a robot. No need to worry about servos and control lines.Of course, it’s not as simple as that. You have to construct the soft outer shell in a way that supports the robot and allows mobility. I suspect there’s also something special going on with the caterpillar’s feet. Again, you’ll have to study the video. The good thing is that the videos — which are of excellent quality — are posted online.

If you manage to get something working, please send in a video or article, and we’ll get the word out. SV

References: Shinichi Hiri et al, Crawling and Jumping Soft Robots, Dept Robotics, Ritsumeikan University, Japan. www.ritsumei.ac.jp/se/~hirai/research/softrobot-e.html.

Michael Simon et al, Visceral-Locomotory Pistoning in Crawling Caterpillars, Cell Biology. 22 July, 2010. You can see the abstract and video at www.cell.com/ current-biology/abstract/S0960-9822%2810%2900807-9.

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