January 21, 2018, 09:33:00 pm
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1
Progress Reports / Re: Team Brain Damage
« Last post by zacodonnell on Today at 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
2
Progress Reports / Re: Twisted Sick Robotics
« Last post by zacodonnell on Today at 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
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Progress Reports / Re: Team Brain Damage
« Last post by zacodonnell on Today at 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
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Progress Reports / Re: Team Brain Damage
« Last post by Koolaid64 on Today at 01:16:10 pm »
I used loctite 609 for retaining my pinions. If you go that route make sure they are where you want them.

-Kyle
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Progress Reports / Re: Twisted Sick Robotics
« Last post by Koolaid64 on Today at 01:14:07 pm »
I just used a three point boring bar. It gave a nice large chanfer on the inside corners. I set up my dials so I know what dimensions I am aiming for and just blind bore keeping an eye on my numbers. I would have preferred the do it with the rotary table but the set up time would have taken longer then I wanted

-Kyle
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Progress Reports / Re: Twisted Sick Robotics
« Last post by zacodonnell 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
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Progress Reports / Re: Team Brain Damage
« Last post by zacodonnell 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
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Progress Reports / Re: Twisted Sick Robotics
« Last post by Koolaid64 on January 19, 2018, 08:54:02 pm »
got my mcmaster order in the other day and started cutting material. I started with roughing out the frame bits of 1/2" UHMW. I then cut out a bunch of blanks for the wheels. I'm trying the bike tread wrap on UHMW rims thing. The blanks are 3" dia and i'm hopping for 3.5" with tread but my yellow tire has not arrived in the mail yet. The rims machined up real easy on the lathe, the inside boring was a little annoying but the finished product looks good and comes it at nice and light 6oz. The last thing I worked on was the main weapon hub. I turned it to size and bored it out for bushings.

I probably won't get to work on anything until this time next week. I'm flying out to Vagas for all of next we for work.

Pictures:




-Kyle
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Progress Reports / Re: Team Brain Damage
« Last post by Koolaid64 on January 19, 2018, 08:05:07 pm »
how do you feel about the brushless drive? have you tested it yet?

-Kyle
10
Progress Reports / Re: Team Brain Damage
« Last post by zacodonnell 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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