Goal of the Jesus Lizard Robot Project
This is the paper they wrote, A Novel Water Running Robot Inspired by Basilisk Lizards. It has all the necessary science and equations useful for imitating the work. If you learn anything from the paper, you should reference the paper. If you learn anything from this webpage that was not in the paper, reference the paper and you can also reference this page if you want.
And here is the official site, CMU NanoRobotics Lab, Water Runner Robot.
What I can offer that those two links do not is pics and video of the earlier work I did on the project, and a quick rundown of the basics. If you do not yet see the videos (and instead see large blocks of white nothing-ness), please wait a few seconds for them to load.
Purpose of this Project
This is slow motion Jesus Lizard video I found on the web that really inspired me:
Video of the Jesus Lizard from Tonia at Harvard. She has spent the last few years trying to understand why the lizard can
run on the water, from a biological point of view. I ran into her by complete accident while visiting her lab for my robot fish project with the Navy.
She was quite excited when she found out someone was using her paper on
Three-dimensional Hindlimb Kinematics of Water Running in the Plumed Basilisk.
Important Facts for Building the Robot
Thoughts on this Project, Control Issues
V1 This video is my first in water test for the 4 bar linkage. It consists of a 4 bar, a large motor,
and batteries as the counter weight. As you can see, it creates both lift and forward thrust. Unfortunately
the low quality streaming video prevents you from seeing the leg on water very well.
clearer image of the foot rotating in the pool:
V3 After proving the 4 bar leg idea works, it was time to build the robot.
This video is version 3 (because styrofoam v2 didnt work), made out of pink foam core and
HDPE. The problem with foam is
that it is not rigid, so the gears kept coming unmeshed. It is also a good thermal insulator, effectively
causing my motor to overheat and sadly fry. The weight was about 70 grams.
V5 Versions 4 and 5 were then made using the technique of transparent styrene vacuum forming. The weight was about
30 grams. Version 5 worked better, so here are two videos of it. The second video was done in water, but the motor wasn't strong
enough to support it's on weight.
V6 Version 6 was similar to version 5 in design, but this time I tried a different type of vacuum forming material. It turns out
the transparent styrene was less likely to crack, but the white styrene looked better . . . The feet were also vacuum formed this time, and the legs
are no longer made from heavy plastic but instead of carbon fiber. Weight was dropped down to about 25 grams.
What is great about vacuum forming is that now I can mass produce the robot chassis.
Here is a cutaway image of the motor and gears inside the vacuum formed chassis. The carbon fiber legs were held together by screws and locktite. Despite the high vibration, the screws did not come off. But looking back, I should have used plastic locking joints instead.
V7 Version 7 is basically the same as version 6, but the weight was dropped to 20 grams and the gear efficiency was greatly improved.
This video was done in black and white, with white marks showing the foot and the joints and the body colored black.
This way I could trace out the exact path the foot was traveling, and use the video frame rate to calculate foot speed at any point.
Towards the end of the video you will see the pear shaped tracing of the foot path.
Two more images of v7. The left image is the traced path using a long exposure time. The right image is from using a stroboscope.
V8 Version 8 is again like version 7, but now the 4 bar linkage was reoptimized accounting for foot angle with respect to the water surface. In this video I tried really hard to get it to run across the water but it just would not stay balanced. It would quickly fall over backwards and instead of running, would swim really fast. As a last minute fix I added a foam balance under it, but with no luck. I couldnt figure out how to design a tail properly for balance either. This was my last prototype - but at least it was shown to support its own weight in the water and worked with the exception of balance! If you look at the foot in the water, you will see the all-important air cavity forming - necessary for a robot to run on water as explained in the A Novel Water Running Robot Inspired by Basilisk Lizards paper. Unfortunately, I did not have access to a high speed camera, so the image is a little blurry. Balance is why I think the four legged design will work much better.
Acknoledgements and Special Thanks
Aubrey Shick for teaching me everything I know about vacuum forming and foam core.
Jason Smoker for help with version 1, and your significant contribution to the 4 bar linkage idea.
Bahareh Behkam for help with the fluid mechanics calculations.
Prof. Metin Setti for being my advisor and sponsoring the project.
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