Project EDGAR

EDGAR(Engineered Dual Gear Auto Recharger) will be my first robot. Very simply, it's a photovore robot taken to autonomous extremes. A photovore is a type of robot that usually uses two bilaterally positioned photocells to determine how to move around its environment. If there's more light on one side it turns toward that light source and vice versa perpetually. EDGAR is more complicated than that:

A design document of sorts.

He's going to be diurnal and charge his battery off whatever sunlight he manages to capture with his photocell. When he's not looking for a recharge he'll switch into a photophobic mode where he looks for a nice dark area to hang out in until his battery winds down to below fifty percent. I also want him to react to movement, sudden changes in light, and sounds. He's going to be a slightly more amicable cockroach compared to the real ones I catch in my kitchen.

A big part of his designed behavior is centered on autonomous operation. Ideally I should be able to plug in the battery and never have to look at him again (Although that would be a little cruel). But, before I get to the electronics and microcontroller I have to build a suitable chassis for EDGAR so he can roll around my apartment in style. I started with the materials I had on hand from a kit I tore apart a few months ago:

Two modified servos and a janky ball bearing wheel.

The first thing I focused on was a suitable way to attach the two servos to the undercarriage with a minimal amount of materials and tinkering. I searched Thingiverse as a first pass because there is no need to reinvent the wheel in this case, people have been attaching servos to things for decades. Of course, I ended up finding nothing that suited my needs to I started sketching my own brace for EDGAR:

The sequence of sketches I went through before arriving at my current brace at the far right. Getting it right on the third iteration was a little surprising for me.

These are my sketches, small prints that comprise only the part I'm working on at that moment. The far left one was my first sketch but did not work because I missed a key notch in the tines that corresponds with an angle brace on the servo:

It looks nice and smooth but doesn't capture the servo mounts!

This then led me to the second iteration, where I put a notch in the wrong tine, which was too narrow to accommodate the brace, and it broke when I was pulling it off the bed of my 3D printer. Overall the worst failure of the group:

The third one though, captured the servo mount and held it in place to the point where I am seriously considering skipping the screws entirely on the final design:

As you can see the notch is on the correct side and I added additional bracing to counter the bending when I slip it over the servo:

Now that I have a set of baller braces for EDGAR I integrate them into a single piece chassis with a small extension to accommodate the ball bearing wheel in the front:

Now he's got some wheels to roll around on. I still need to fix a few things though. Right now the top platform is 2mm and deforms enough that I'm worried about overall stability so I'm going to up its height to 4mm, which will force my printer to add a nice honeycomb support structure to the interior. Overall, I'm very happy with how the chassis came out. There's still tons of work to be done so stay tuned!