My 4DoF Quad Mech: Numa

[Gertlex]

I mentioned other parts. These were tiny brackets for a hinged clip mechanism for holding sideplates onto Numa. The sideplates will protect various electronics and securely hold the 9V battery for the Axon

I 3d printed some of the parts (yellow) and cut out the other from delrin because they were too small to print nicely. I chopped up the springs from a couple of pens, as well. These contraptions add maybe 20g including the carbon side plates. These things are small. The top yellow pieces have a base of like 1x2cm.

Additionally, a pic showing the inside of Numa... completely packed; and a pic of my current turret design as of earlier today. It's all stuff I can do with the dremel using delrin. (4 weeks to iHobby!)

[Gertlex]

There's a bunch of pics of the turret at http://www.flickr.com/gertlex

And today, printed and fitted hopups (they work!). Besides coding, the only thing left to do for iHobby (in two weeks) is finish the left hopper and secure the hopups in place...




And Numa doing pushups... turret range is kind a limited and the guns are pretty high up, so this might be helpful against bots that get really close to Numa.
http://www.youtube.com/watch?v=GATkjccJuBk

[Gertlex]

Two weekends ago, I went to iHobby with cire, Immortal, and Numa. Things that went wrong:
-Burned out two AX-12s, a 3rd one probably has a bad motor. (More on this later)
-One AEG motor killed itself (cire has one that did the same thing at some point in the past)
... but I had spares!
-And then my laptop's charger died (laptop's battery isn't good for 2 mins)... of all the things to die... I was able to borrow another guy's laptop and use X-Ctu + IE for control+vid.
-Numa is very tall, and doesn't have as much tilt range in the turret as is needed for bots with very low mounted score panels
-AEG/hopper setup had lots of misfires; working on fixing this.

Things that went well:
-Party at Trossen on the Friday evening
-Got Numa's IK walking working properly at said party (like at 1am)
-Numa walked pretty well
-Won one match out of 6 against Immortal... cause immortal had a leg servo die
-Shot at kids because they asked me to (arena wall between them)
-Bought a spare lipo at the show, as well as a 2S 380 mAh battery to replace the NiMH batteries I've been using to power my microcontroller.

Major thanks to Mike and Tim for doing the arena and being good chums. Thanks also, Mike for all the video footage =)
Here's a good one of Numa's walking, as implied above, this is pretty much the IK walking without more than a handful of initial tweaks...:
http://www.youtube.com/user/moverstr...35/SterwHkoPT4
(This is also when the 3rd servo died on me)



The first AX-12 died while I was working on getting the IK right. I had a bug in my foot-height code that meant the legs were basically slamming into the ground when switching which pair of legs is on the ground whilst walking. The AX with the probable bad motor was found at the same time - it moved as told, but i could move it by hand when it was powered, too.

I'm focusing a bit more on grad school currently, but I aim to redesign the turret for more range of motion and better feeding of BBs. One quick mod I'm playing with is a piece of copper wire going into the hopper to act as an agitator. It's attached to one of the external springs on the gearbox:

[rebel]

Nice fix with the spring, i might try to use

[Gertlex]

So two months of progress for you guys... but really not that much. Grad school, alas.

Physical additions to Numa include:
-second battery monitor for 2S lipo (looks nice having two of them on the front of Numa)
-two Sharp IR rangefinders mounted to the sides (gimmicky proximity sensors that will let me see if I'm too close to a wall...)
-used up all of the wire sheathing that I had to tidy up the wiring
-Changed the feet to use different brackets -> easier walking on carpet and better balance
-Working on getting a whole new set of carbon fiber parts made some of the leg joints will be carbon fiber
-Tested yellow dye for bioloid brackets... gotta get a better yellow (namely Neon Yellow RIT dye, rather than Golden Yellow RIT dye)

I've still got to do the turret redesign. And I burned out another servo's motor, but I'll blame the carpet for that.

And software... lots of work with the command/control stuff. The big thing is that I can now control Numa with an Arbotix Commander... and I'm not using an Arbotix . I had to make some fairly straight-forward changes to the Commander.c and .h files so that they work with Axon/Webbotlib variable names. Props to fergs for the Commander communication protocol.

I've also somewhat smoothed the speed changes, but still a bit jerky - not sure if it's a bug, or a limitation of the methods I use. The method works fine in Mathematica! (Basically I track time for the IK with a triangular wave... if I change the frequency (aka Numa's walking speed) of that wave/function, I have to account for two speeds being out of phase, and adjust accordingly)

[Gertlex]

Some updates!

I successfully did the dyeing, after all (details are in the bioloid dyeing tutorial). Result so far is... so awesome:

(I've gotta dye the feet brackets, but I'm trading grey brackets for white brackets with cire, tomorrow)

The middle leg joints will be replace with carbon fiber... I put my order in this week with Big Blue Saw (leg brackets, new chassis and side plates, whoo!). Downside is, not cheap, and they're not even doing all the 2mm holes in carbon fiber for me (wtf). I'll do the holes myself, fairly painlessly, with aluminum templates that are also getting cut... I was lazy and didn't shop around.

Got my plane ticket to Robogames, too. (It's been an expensive month.)

I redid my turret linkages. Instead of about 40° of tilt range, there's now up to 70° of tilt possible. I've also got nylon spacers that are now dyed. Some of them also have holes and set screws in them. Bunch of pics:



(In case you wondered, the long shiny rods are how I mount the AEG gearboxes)

I can also now control Numa with the Arbotix Commander plugged into my computer, and an xBee plugged into my computer. This allows Numa to send data back to the computer, and the computer forwards the Arbotix Commander signals to Numa. If I want more portability, I just put the xBee on the Commander, and I can do stuff sans computer.

What data does Numa send back? For now it's just two Sharp IR rangefinders that are mounted on the sides. These determine the color of two sidebars next to my video feed... And I've adapted Upgrayd's python based Trendnet viewer for this purpose. The python program also does the forwarding of the Arbotix Commander commands through to the xBee; this does induce some lag, but I may be able to fix this with threads or just running two separate programs.

I've got a vid below that demos the IR rangefinders, Trendnet viewer with colored sidebars, and a bit of walking.

http://www.youtube.com/watch?v=lgcCU-LWUdY

Next up, I need to redo the hoppers so they're actually attached to the gearboxes. The turret redesign saved about 15 g... redoing the hoppers should save another 30-40 g (those sideplates on the turret are heavy). The weight saving is mostly just a secondary challenge, but I like to keep track of it . I don't use carbon fiber on the turret because CF can block wifi signals...

There's also plenty of programming work to be done... mostly on the IK, which is not as smooth as I'd like; it might just be I need to spend lots of time calibrating so walking is better.

[gdubb2]

Looking good...The rangefinder info is cool.. not too sure how much they will help, but cool..

Gary

[Gertlex]

Looking good...The rangefinder info is cool.. not too sure how much they will help, but cool..

Gary

I implemented them as a gimmick sort of thing - in a mech, one has flashing warning lights everywhere, right? I also had problems walking too close to walls at iHobby, but I suspect the non-funky buildings at robogames will give a better sense of side-to-side position in a 'street'.

[Gertlex]

So I've reassembled Numa now that I've dyed everything... even dyed the trendnet camera case, which shrank noticeably.

Oh right, and I had a bunch of carbon fiber parts waterjetted - new chassis plates, leg brackets, chassis side plates, and Arbotix coverplate (for the heck of it). The main cuts were waterjetted, while I did all of the 1/8" and 2mm holes myself. Drilling holes with dremel doesn't shoot carbon dust everywhere, so the waterjetting was nice for my in-apartment fabrication...

I 3D printed 3-part pieces for the feet that span one of the bracket types.

Still gotta fix another bug in the IK.... Also, yes, there is a foot servo that is not plugged in below, whoops!

Hopper redesign is a work in progress. My biggest concern is reliable feeding into the AEGs. I hope to sheath the rest of the wires on Numa, but that's the most tedious thing ever. Scoring system is going to be a hat that's easy to remove from the turret, and won't look amazing.





2 Months to Robogames. Oh geeze. In addition to everything else, I need to get a Pelican case and a suitcase...

[Gertlex]

Well! I successfully completed Numa at Robogames Which is to say, I had everything done except mounting the lighting board when I got to Robogames. Numa was nice and reliable, and got 3rd, despite only scoring 9 hitpoints of damage or so. :P

I ended up redoing my hoppers completely, with reasonable improvement. I did the first gun about 3 weeks before Robogames; the second one a week later, but was a bit more prone to jamming. I basically chopped up two Crosman guns for the 'hopper rails', and then built polycarb hoppers onto those. The rails feed into the 3D printed hopups.

I also added an 'unjammer' for both guns, actuated by a single HS-55 servo (driven by hardware PWM on the Axon). I suspect that having it cycle back and forth (see youtube video) multiple times was a poor choice in that it probably packs the BBs in after the initial poking.

Zero AX-12A motors burned out, amazingly. (I have 5 that have burned out motors…) I think this was mainly due to my adding a crouch mode where torque is disabled in the joint closest to the body. Additionally I made the foot height transitions a bit “smoother”. Finally, I stopped sending the stand pose continuously since someone suggested this might be a culprit of burned motors (still not sure I believe this). But ya, did what I could to avoid burning servos, and it paid off I guess.

Crouch mode did inadvertently lead to Numa tipping during exhibition once: Pushed backwards while in this pose, the back legs curled under the body. When I tried to stand again, the legs were stuck under the body, so the rest of the robot rotated, instead of the back legs. Just something to work around

Various other tweaks and things learned over the past two months
-I did sheath all the wires. I also had dyed some of the 3pin connectors yellow, and was replacing connectors as I went. The connectors shrink a tiny bit, enough that the connections can be unreliable.
-I had plugged in the signal wire for the tri-state buffer wrong when I reassembled the chassis a couple months ago... I discovered this two weeks before Robogames. It caused very unreliable communication with the servos for obvious reasons...
-Series 2 (aka ZB) Xbees are to be avoided. Thankfully I had a spare set of Series 1 Xbees. The former are slow to connect and will occasionally drop out.
-Aiming is important… lasers definitely helped other bots, and (at least with Trendnets) are easy enough to see. Definitely adding the lasers that Trossen sells for next year.
-I replaced the 9V battery with a 2S Lipo, which powers the Axon and scoring system. Correspondingly I have a second battery monitor - you can see both of them as the blue LEDs on Numa's front side in the previous post.
-Somehow my 2S battery monitor's blue LED no longer works (broke at RG). Haven't investigated this yet... but it still beeps when I turn the battery on.

Numa will compete next year too… I’ll tweak/improve various stuff, and probably redo the turret/guns/camera again.

Hopper unjammer: (sound is horrendous)
http://www.youtube.com/watch?v=Bo5a3qFCYS8