August 16, 2018, 08:16:00 am
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Messages - zacodonnell

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31
Progress Reports / Re: Team Brain Damage
« on: February 06, 2018, 09:45:57 pm »
I think I traced the drive issues to a loose receiver wire on that drive controller. I was able to reproduce it by tapping on the wiring harness / controller while trying to drive. At first I thought it was something internal to the controller, but when I went to swap the controller out I found an untaped rx wire extension in the chain that had the connector mostly pulled out. My extensions have a little plastic clip that is supposed to hold the parts together, but I always tape them anyway. Looks like that's a good plan as this one appears to have separated just from my test flips. I got it put back together and could no longer reproduce the problem on the bench.

I moved on to planning out the updated cleats that will hopefully not bend the frame as much. They're going to be angle brackets that share the load between the front and side rails and extend much less far from the robot. I'm hoping that with good cleats I can actually cut the outriggers way down, which would give me better reach on the opponents as well as providing the weight for the beefier cleats. I'll work on that tomorrow or Thursday. With any luck the snow will force work to cancel :)

-Zac

32
Progress Reports / Re: Twisted Sick Robotics
« on: February 05, 2018, 09:05:51 pm »
What adhesive did you use? And how much diameter did the tread add? They look grippy :)

When my drive setup is working, it's way more power than the wheels are putting down. I long for more traction, but don't have any weight or time to do something like this. Perhaps next time if it works well I can, uh, rip off? your design

-Zac

33
Progress Reports / Re: Team Cosmos
« on: February 05, 2018, 09:03:14 pm »
This is gonna be great! I have brought a shell spinner to Motorama I think every year since 2004. There's some sweet irony in the fact that 2004 was the last year Killabyte competed there, and that I am unable to bring Triggo this year. It's like the essence of the shell spinner is passing back and forth :). I'll definitely be rooting for it to put on a good show.

Can't wait to hang out with everybody

-Zac

34
Progress Reports / Re: Team Brain Damage
« on: February 05, 2018, 08:57:39 pm »
I agree, it is being a bit frustrating. I didn't have any time to work on it last week either. If I can't get it to be pretty reliable before the show I'll swap the old setup back in and try again next time. My biggest fear is thinking it is working and having it flake out on me during a fight.

Hopefully more to come on this tomorrow night.

-Zac

35
Progress Reports / Re: Team Cosmos
« on: January 29, 2018, 10:20:36 pm »
Looking forward to it, since I'm too lame for Facebook :)

-Zac

36
Progress Reports / Re: Team Brain Damage
« on: January 29, 2018, 10:19:26 pm »
More work on the bot tonight. The left side drive system is still giving me fits though. The right side has worked this entire time, so I'm starting to suspect it's specific to either the wiring harness for the left side or the controller. I have a couple of backup controllers to try, so I'm going to swap one of them in and replace all of the signal wiring between the controller and the receiver for good measure. I prepped the backup controllers tonight and the glue is drying now. Here's a testing video with some comentary. Toward the end I started to think it was mechanical instead of straight electrical noise...
https://youtu.be/Xd7sWcAbFAs


The outriggers are bending already, so maybe that weight reduction hole in the front was a dumb idea. I'm going to try to remake the cleats as pieces of angle tucked in the front corners to try to take some of the leverage off of the outriggers. I tried a flip without cleats but that was pretty scary. All I can say is Hooray for Lexan! This is the reason I have a door on my test box :)
https://youtu.be/miDasiB7Heg

-Zac

37
Progress Reports / Re: Team Brain Damage
« on: January 28, 2018, 07:45:05 pm »
I tracked the issues down. It was painful and time consuming, but eventually I was able to get one-wire programming of the controllers to work from my laptop. There was some wrestling with the drivers and settings involved but in the end I'm happy with it. I still need to prep the other two controllers I got as spares since I'm sure the motors could do bad things to the controllers if they get jammed up.

I did some more weight reduction this weekend too. Hollow front axles, shorter drive axles, and remade the side rails with more pockets. I even put a 1" hole in the outriggers now that I know 1.5" thick outriggers were *almost* enough (after balhogs chopped my existing ones in half)

Adding up all the bits of the bot (didn't have time to assemble it) shows 29.996 lbs.  Not too shabby!

-Zac

38
Progress Reports / Re: Team Brain Damage
« on: January 23, 2018, 09:47:22 pm »
A little more fun with programming the drive controllers tonight. Need to actually make a change that I can verify as it seems like the tool reports success even if I don't attach a controller.

-Zac

39
Progress Reports / Re: Team Brain Damage
« on: January 23, 2018, 08:37:58 pm »
I decided to try calibrating the drive speed controllers with my transmitter stick to see if that would help before I rip them out of the bot and redo the settings. I'll still probably have to do that because I didn't change the low voltage cutoff and I'm running 5S A123, which might look like a really tired 5S lipo or a healthy 4S lipo to the controller. I don't want it "saving me" and costing me the fight.

The calibration made a huge difference. Before I did it I could easily get the left side drive to stop working. It was like it lost the signal from the rx and wouldn't pick it back up. Even turning the bot off and back on didn't always bring it back. I think the neutral signal from the tx was on the very limit of the arming line for the controller, so it didn't spend much time "in the window" to re-arm it. Playing with trims and the like didn't help much, though I could sometimes get it to start going and then stop.

Once I redid the calibration (one side at a time, still with mixing turned on in the TX) it seemed to fix the problem. I did a 2-3 minute test with the weapon pod out of the bot and it performed fine. My little wimpy test box isn't big enough to actually test it, but I could drive back and forth trying to not hit the walls or the end. I'll need to practice more to get used to it. I turned the steering channel down to 50% to avoid oversteering and that helped a lot. Spinning in place with the flywheel going and the steering channel all the way up will be some kind of silly gyro dance I'll bet.

video:
https://youtu.be/UE2u8fXp_nU

-Zac

40
Progress Reports / Re: Team Brain Damage
« on: January 21, 2018, 08:45:51 pm »
Ok, initial flip and drive testing is done. The flips are a little weaker than I want, but I think that's because of the cleats and frame being messed up. I have to replace the side frame rails to fix the damage done by the Balhogs saw bot last year.  The sensors work well and turn the magnet off ~11ms before the arm strikes the rubber stoppers on the frame. I've done a little more tuning since I made the video to make that window as small as possible. I put a white stripe on the flywheel so I could see how fast it's going. Mostly for academic and efficiency reasons - no practical implications yet. Someday I'll actually use the info probably.

The robot also self rights reliably, even at very low speeds, which is great. The sensor should reduce the over-throw on the self right attempts and prevent wasting the entire flywheel when I do it.

Now the bad news:
The drive system is flaky. The left drive motor seems to lose track of the signal and stop working intermittently. Sometimes a power reset fixes it, sometimes not. Sometimes it never connects, and other times it is working for a while and then stops. Could be a loose wire, but I'm betting it's an issue with the radio signal and the controller being picky about arming. I also have witnessed a few "runaway jitter" scenarios where the motors start jerking forward and back semi-randomly. They seem to come when spinning up the flywheel most often, but not always. It could be some kind of electrical noise but it is really bugging me. I'll play with the signal leads and extend the deadbands on the controllers to try to fix it. If I can't in pretty short order, out they come and back in go the old 550 motors. When the drive is working it is WAY FAST though. My little 4x8 test box with a dusty floor doesn't let me really see though.

I'm also about 5 ounces overweight right now. I knew it would be over, but I was thinking 3 or 4. I think I can still find the weight, but yuck. Worst case I could go to lipo batteries for moto, but I want to make sure the new drive motors work out before I do anything drastic.

Walkthrough video of some of my testing:
https://www.youtube.com/watch?v=Izz1zTKJPUk&feature=youtu.be

And self righting:
https://www.youtube.com/watch?v=At8CjyNKJIw

-Zac

41
Progress Reports / Re: Twisted Sick Robotics
« on: January 21, 2018, 03:09:51 pm »
I'm not sure I understand. Remember, I'm a computer geek, not a machinist :). Were you using a mill or a lathe? I have a single point boring bar for my lathe, but I can't see how the three point version would work in a mill without a rotary table. 

-Zac

42
Progress Reports / Re: Team Brain Damage
« on: January 21, 2018, 02:20:01 pm »
Thanks. I got it all installed and have done just a couple of tests. I didn't put any retaining compound on it yet, but I added it to my next order. Might be a little tricky to get the gearbox grease off of the parts before I use it - any pointers there?

They are WAAAY faster than the old setup, but I think I need to increase the deadband in the middle of the controls because it is tricky to get them to zero out and arm. It also seems like they don't both do it at the same point so I have to mess with trims a bit. When I set a dual rate on the steering channel it made the problem worse, and I am also seeing some jitters from electrical noise when I push the weapon throttle up. I'm hoping a wider deadband and some calibration will help all the problems.

I'm going to mess with some settings and put the little noise filters back on the wires and see if that helps, but the way it is now isn't workable for the competition. Slow and steady is way better than fast and unreliable for me. I've spent most of the day testing the weapon sensors and timing. I have a lot of high speed video that I'm using for analysis. I'm going to keep messing with it for a bit but I'll publish out a quick rundown once I make some more progress.

-Zac

43
Progress Reports / Re: Twisted Sick Robotics
« on: January 20, 2018, 09:01:36 am »
How did you do the internal cut on the UHMW? Rotary table on the mill would make it a breeze, but on the lathe isn't it hard to keep the chips cleared out inside the bore? Did you just make a square HSS cutter? I really like the idea of that kind of wheel.

-Zac

44
Progress Reports / Re: Team Brain Damage
« on: January 20, 2018, 08:58:22 am »
I haven't tried the brushless drive yet. The torquecalc says it should slip the wheels around 36A, which should be right at the peak efficiency of the motors and right in the wheelhouse of the 70A red bricks (I hope). I haven't done any real tuning on the simonk firmware so we'll see what happens. Did you use any kind of retaining compound on the pinions on your motor? I'm not sure the press fit is going to be man enough for the bigger motors. I was thinking something like Loctite 641. I'll try without and see if slamming the sticks back and forth can throw the pinions.

Backdriving the assembly by hand sure feels smooth compared to the 550 motors, and the build quality on these is WAY higher, obviously.

-Zac

45
Progress Reports / Re: Team Brain Damage
« on: January 18, 2018, 10:33:15 pm »
Today involved a little work on my house instead of my robot. It is all squared away now, and I managed to get the keyway cut on the new weapon motor too. The glue set nicely on the drive motors so I'll be pulling the old ones out and replacing them, as well as installing the new weapon motor this weekend. I did break an endmill but I had a spare (thankfully)

Pictures:
https://plus.google.com/photos/107279152885550274671/album/6510901572747399649/6512596638728282226

-Zac

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