When your baby is learning to walk, you make sure its near soft things and away from stairs so that when the inevitable fall occurs, they don’t collapse into pieces. When your baby is a robot learning to walk, bungie chords and harnesses are also needed. And in the case with noodle, who is delicate and wobbly like a skittish baby fawn, I am sparing no precaution!
The noodle Harness
Robots get rigging. Mark took the time this weekend and installed a guide wire on the ceiling over our work table. A “leash” hangs down from this wire and clips on to noodle’s smashing neon-yellow harness which wraps around all four of his legs. If he loses his balance, he won’t have very far to fall before the leash pulls tight and catches him.
Before assembling noodle for his big day, I had to calibrate all of the servo motors to 90º. Only then could I screw the gears to the motor shafts, as well as connect the pulley bits from the secondary servo motors on each leg to the bendy bits.
In the end, once all of the final parts were attached to one another, I was pleased with how solidly he stands on his own. Hopefully I can figure out the right way to distribute balance so that he can lift up his feet and walk.
Wiring up the Bread
Lastly, this afternoon I taped an Arduino down to the end of a breadboard and fashioned some male headers so that the servo motors could easily plug-in and tether to their appropriate pins. The breadboard itself is taped directly to the leash so that it will move with noodle as he walks… or falls.
When is he walking?
So, he’s poised and ready. The big moment will either come tonight some time or tomorrow after Mark is home from work for the weekend. Either way, I’ll be sure to take LOTS of footage of my wobbly child as he navigates across the table for the first time. =O
Wish us luck!
Last week I started building a new robot who I’m calling noodleFeet! He is essentially a spider-type walker who will locate nearby legs, approach and then lean on them. In addition to having that specific purpose, he needs to look a particular way. I’ve been drawing him in the margin of my notes for weeks now, so he’s become something of a character to me:
In order to make a robot that does these things, I need to design the mechanism itself and how it will be attached to the motors driving the motion (challenging and fun). At the same time I need to learn about Open CV and figure out how to make a computer recognize all the different shapes that legs come in. This will involve a camera and some coding (hard and not fun). With these two elements combined, I’ll eventually end up with a leg hugger…… or leaner. I’ll talk about the details of those steps when I get to them.
To get started, my challenge for the weekend was to solve how to make the legs of the robot itself. I wanted to come up with a reverse knee-joint capable of folding into a single-stick. This took about three of four revisions to get right, at which point I went on to 3D print four copies for the proof of concept.
The proof of concept is nothing more than a rough servo bracket that holds all of the motors in place at the point where the four legs attach to them. With these parts alone I was able to construct something that looks surprisingly already very much like the end product I’m aiming to create. It still isn’t a working prototype however. For this, my concerns were mainly measurement and proportion:
I’ve gotten away with using 3D printed parts on many of my projects, but for this one plastic isn’t going to cut it. Even though the design is mechanically sound (I believe) and I could have wired some servo motors up to see some motion, the flimsy plastic legs don’t seem like they’d be able to support the combined weight of the motors… so I didn’t. Because of that, the next step is to replace the crucial parts that support the most weight with aluminum pieces. So I’ve gone ahead and ordered some hollow pipe and bearings for a more sturdy, motion-ready second prototype. In fact… the materials arrived today, so it’s a good thing I got documenting this out of the way!
Hopefully with my next post I’ll have video of noodleFeet making his first steps… or wiggles. You can see him in this illustration I recently drew to the right of our car: