I am interested in exploring BEAM robotics for my solar assignment for Energy class. BEAM, to me is fascinating in its biomimeticness and in its handicraft nature of free-form circuit sculpting. I am on a biomimetic / fake nature trip this entire semester. These themes are recurring in two other classes I am taking on soft robotics and micro biology exploration. I am eager to see how all of these could come together down the road.
So for this particular assignment I envisioned a BEAM based underwater robot. This is one category I found to be quite under explored in the BEAM circuit (:p). I looked through several BEAM maker forums but didn’t find any documentation. I decided to build my own based off a simple solar engine. The engine uses a capacitor to store charge from a PV panel and runs it through a voltage comparator and transistor to dump the charge into a single motor once the voltage from the PV rises to a particular potential.
This is the engine that makes the robot work. It takes in power from the PV panel on one end and a motor is attached to where the alligator clips are. I thought, once I get the motor to move, I can use it to actuate any kind of mechanism I design beyond that point. I was envisioning something to the effect of a deep sea organism. Very delicate, elegant and mystical!
Pictured above is FESTO’s smart inversion drive system, where a geometric floating object (inspired by origami toy) is filled with Helium and propels itself by inversion.
This, combined with a jellyfish was kind of the mental mood-board I had created.
With these references in mind I set out to ideate on the robot’s form, structure and mechanics.
These are some of the early explorations. I eventually hit upon the idea of using a spring shaft as my main drive system. This is commonly found in the Dremel tool kit and as flexible extensions for power drills or screw drivers.
Hardware and parts
- 15″ Spring shaft, hacked off a ‘flexible gripper’
- 6VDC gear motor
- 2mm metal shaft to extend the motor’s axle
- 4V circular solar panel
Everything else was found on the ITP junk shelf.
First thing I had to do was test the spring drive working principle. I cropped a segment of the spring off the gripper, taped it with a pin at the center and tried rotating it manually. It worked! and it was enough to create some conviction about the idea. I just had to figure out how to drive it with a motor.
Next step was to extend the motor’s axle. I wanted a dual shaft so I could attach both ends of the spring drive to the same axle. In this case I had to reprint a spur gear from the motors gear box for it to hold the new extended axle.
I remodeled the gear in CAD and got it printed.
Next, I glued the spring drive to both ends of the motor. Instead of rotating or inverting, the spring drive was spinning with the motor’s axle, making full circles around the motor. I realized I had to constrain it’s motion in vertical direction to keep it from revolving around the motor and instead make it rotate around itself.
I made the necessary modification to the CAD file (pictured above). I also designed a basic casing for the motor and the solar engine and put it for 3D printing. In the meantime I started working on making a jig to glue the linkages to the spring drive. The linkages were to be glued at 90 degree angles alternately.
Parallely, I started working on sculpting the solar engine. This is the best part of the process for me. Free form sculpting of electrical components is an art. You have to carefully plan out the entire architecture and carefully bend and route the wires for soldering. Doing all this with just two hands makes it more challenging.
It was time to put it all together. After 4 sticks of hot glue it finally came to life.
I could manage to record it just before the motor axle slipped on the 3D printed gear. For this reason I dint continue with attaching the flaps. This is also pretty far away from actually being water ready. I plan to keep refining this idea as and when I get time. The idea for this kind of radial drive is proven mechanically. Now its a matter of making it waterproof and perhaps scaling it up in power to see if it actually propels itself underwater!