Thursday, August 8, 2013
While this Instructable won't actually tell you how to build the real thing (which still requires a lot of expensive laboratory equipment), it will show you how to make a paper model of a RoboBee. This is something engineers in the lab do all the time - real RoboBees are pretty tiny, so having a larger paper model helps them think about mechanical design and how all the pieces will fit together.
The secret to making RoboBees involves using lasers to cut shapes out of flat materials, and then folding or "popping up" these flat shapes into three-dimensional structures. The following video by Pratheev Sreetharan provides a great introduction to the "pop-up" technique for building RoboBees. In this project, you'll be cutting out 2D parts and them folding them into 3D shapes by hand, so it won't be quite as automated as the process shown the video.
Materials8.5"x11" sheet of cardstock. You need at least one, but can use different multi-colored sheets if you want. Regular construction paper will be too flimsy. Craft glue (regular Elmer's glue will work fine) There are three options for cutting out the parts: Option 1: Xacto knife, cutting mat, and a steady hand Option 2: Electronic cutting tool (I used a Silhouette CAMEO) Option 3: Laser cutter, if you have access to one. Be sure to follow all proper safety procedures and do not use a laser cutter if you are not trained on its use - they can start fires or generate toxic fumes. Design file: available for download below as a .pdf or on Thingiverse as a .studio (proprietary format for the Silhouette CAMEO - Instructables wouldn't let me upload it). If I get enough requests I will redo the drawing as a .dxf or .dwg - so far I haven't been able to export these formats from Silhouette Studio (feature request in case anyone from Silhouette is reading this!). Optional: 2D CAD program, if you want to try out your own designs and are using an electronic cutting tool or laser cutter. There are multiple free options out there - I've used DraftSight (which was free last time I checked) and I believe you can also download a free student version of AutoCAD (may require creating an account). I know Autodesk has a bunch of new 123D apps, but I'm not sure if any of them are exclusively 2D programs that will output a dxf or dwg that you can use with a laser cutter.
Credits: These directions were written while I was a postdoctoral researcher in the Cornell Creative Machines Lab. The RoboBee project was started at the Harvard Microrobotics Lab. For more information and technical details about the project, you can check out the lab's publication page or YouTube channel. You can also check my personal publications page, which includes my Ph.D. thesis on body torque actuation. To see some more awesome engineering work on functional robots made out of laser-cut paper, check out the Berkeley Biomimetic Millisystems Lab.Before you start building a paper model, you're probably wondering how exactly a RoboBee works. Here is a really quick, layman's-terms explanation of the four main parts, which are labeled in the picture above. Airframe: this is the robot's "body". It's the rough equivalent of an insect's exoskeleton. Nothing super high-tech here - it's pretty much just a box made out of carbon fiber that holds all the other pieces together. Actuator: actuator is the engineering term for "thing that causes motion". In machines, actuators are usually motors or engines. In animals, actuators are muscles. In this case, the RoboBee is actually way too tiny for a motor - so we use a piezoelectric material, which deforms when an electrical voltage is applied to it. A piezoelectric beam bends back and forth as this voltage changes, acting like a "flight muscle". Transmission: this is another engineering term. The transmission converts the back-and-forth motion of the tip of the actuator (which is roughly moving in a straight line) to the rotational motion of the wings. It's hard to see in the picture here - this will make more sense when you build your paper model. For now, think of it like a linkage built out of LEGOs or K'Nex, if you've ever played with those. Wings: This is the most self-explanatory part. The wings flap back and forth to generate lift, which is what makes the RoboBee fly. More advanced versions of the RoboBee have multiple actuators to independently control the wings, which allows them to steer.
1 Tbs. sugar
¼ tsp. salt
1+ cup all-purpose flour, sifted
1 cup milk (I used ½ cup evaporated milk + ½ cup water)
1 tsp. vanilla
2-3 quarts canola oil
Deep fat fryer (or a heavy sauce pan and thermometer)
Fork or whip
For anyone trying to build propane flame effects, there is a critical element which needs controlling: a solenoid valve. Solenoid valves are basically electrically controlled valves. These come in a variety of different versions depending on your voltage / polarity requirements. Fenrir uses 120V AC solenoid valves. In short, connecting 120V to the 2 lead wires of the solenoid valve opens the valve. Disconnecting voltage from the solenoid closes the valve. I got my solenoid valves from ebay seller valves4projects (http://myworld.ebay.com/valves4projects/)
SAFETY NOTE AGAIN:
If you buy solenoid valves from anywhere for use with propane, make sure they are properly rated for use with propane. Water valves will *NOT* work. They will degrade...you will hurt yourself, or something will explode. Valves seals should be viton. Valve bodies should be brass or stainless steel. Valves should be rated at 200psi or greater.
To control the valve, we'd like to use microcontroller to do the RF sensing, and the opening and closing for us. A microcontroller is like a miniature computer that can't do a lot. Actually, I tell people to think of microcontrollers as little gremlins that you can poke with a small electrical current and they will flick a switch on or off for you...its a bit closer to reality. Arduino is a really popular and useful microcontroller if you are familiar with those. For this project, we are going to be using Pololu's Wixel instead (http://www.pololu.com/catalog/product/1336)