pic: FRC488 - Team Xbot's 2009 Robot

Video of a systems test: http://www.youtube.com/watch?v=_gpkF8Ptau4

Taken at the practice field late Saturday night. The black paneling is temporary and will be replaced by polycarbonate sheathing with our team identification on it. It will continue to be opaque, though.

Some information:
– 4WD with 1 CIM motor per side, geared at about 8:1. We have “traction control on demand” for straight line acceleration but have found that our drivers like the robot to be a more loose in the turns.

– Conveyor features front and rear, independently driven urethane belted mechanisms, each powered by a FP motor geared at about 39:1. We can load empty cells from the floor and store them in the conveyor and are able to return them to our payload specialist.

– Hopper capacity is 20+ balls and it can unload in 2/2.5 seconds. The hopper is itself a fabric “bag” that is rolled up on a drum to raise its floor to the top of the robot. It is powered by two CIM motors at 8:1, though we’re considering speeding it up some.

Very nice! I like the bag idea… I take it that was the redesign you posted about a week or two ago?

It seems to work very well… gotta run… FedEx is here.


The major mechanisms haven’t changed since kick off, actually. The structure that supported them, however, was completely rebuilt a few weeks ago. So, while we’d always intended to use the fabric hopper, the frame that it lives in was not designed well enough to deal with the troublesome nature of the balls the first time around. It’s now considerably more stout and the balls move freely through the robot regardless of number.

Part of me expects your opaque hopper will cause you to accidentally (albeit rarely) incur <G24-A> penalties. Are you counting on it being offset by the fact that referees will have just as hard of a time determining if you are in violation?

The thought has crossed my mind. The front panel will likely become transparent as a consequence and that should allow our drivers to be sure that we don’t have more than one empty cell in our possession at once. We’d like to keep the hopper opaque, however, so that other teams have a more difficult time keeping track of how many balls are in our possession.

That is an impressive video you guys uploaded. How many balls can you store in the “hopper” and on average how many of the loaded balls make it into the trailer. Looks awesome! See you in Portland.

Thanks! Your robot looks pretty nice as well. Hopefully we’ll get some chances to play with y’all in Portland and Seattle.

The hopper can hold 20 balls. Our testing shows that the number of balls that make it into a trailer depends almost entirely on our distance from the trailer. Maybe saying as much is obvious, but it really makes a big difference. In ideal conditions, 95% of the balls make it in and the accuracy drops from there as the distance increases. :slight_smile:

I have some video taken at the practice field that shows us chasing around an older robot and scoring on it as well as some that demonstrate our traction control algorithm. I’ll try to upload those to our YouTube account tonight – but some of them are pretty uneventful and boring.

Nice work 488! I like the approach that you have taken to unload the balls quickly. I am looking forward to seeing it in action in a couple of weeks!

I wanted to update this thread with some videos I’ve just added to YouTube.

They’re not fancy, so don’t expect funky music or titles or anything like that.

The first shows about two minutes of driving, collecting and scoring. We learned pretty quickly that chasing down a single robot and scoring on it was extraordinarily difficult. We expect that it’ll become quite easier to find targets to score on when there are more robots on the field. It was also to get a feel for how many balls will be available for collection from the field since our supply was limited and there were no human players.

We broke an encoder early during practice due to some misalignment, so all of this driving was done with half-broken traction control. The right side drive had traction control and the left side did not, so the robot was very hard to control.

The second (eventually) shows off a bit of the rough traction control code and was taken before we broke the encoder. We’ve opted to make traction control controlled by a joystick button such that it’s on only when the driver wants it. As we refine it and make it respond better in turns, we’ll turn it on permanently, I expect.