How goes the build?

[MrJohnston]

This is a follow-up on a poll I did three weeks ago - I was going to do this last week, but got kind of busy....

[AustinH]

The core mechanisms work well enough for week 4. Still waiting on the results of prototyping to determine some extra appendages. Meanwhile, the programing department is (at my egging) having fun with gyros and PID loops. The desired target is at least one full week of drive practice with a finished robot. We don't have the cash for a practice bot this year, so every singe day counts.

P.S. Has anyone come up with an elegant solution to the gyro roll-over problem (going from 180 immediately to -179 or 0 to 360 and spinning in circles)?

[mrnoble]

We're trying to get the comp bot ready for powder coating by friday, but we've got to get all of our superstructure attachments finalized before machining the final pieces. 1/3 of the mechanisms is mechanically complete; 1/3 is tested and final parts are being constructed tonight; 1/3 is CADed but needs to be built.

[Sperkowsky]

We are kinda in a rough position. Because we have no access to cnc, milling, 3d printing, 8020, or even square aluminum tubing we have to build everything out of bar stock and I bracket. I very economical but very annoying thing. We are almost done with the frame. Have about 4 Major holes to drill and like 16 more nuts to tighten. From there we can put in the elevator but being we haven't even mounted any pullies yet we have a lot to go. The good thing is we do have very good coding and electrical teams we are almost done with electrical (we are making it really tiny I mean crazy so) and coding was done week 1 (including tuning in the mecanum wheels)that is other then making the elevator go up and down. So yea we are doing alright but it's. Going to be close and I doubt we will get any driving practice. We still have to mount all the elevator mechanisms including like 8 pullies and we also need to build the lift arm.

Hopefully next year will be different now that we have sponsors but it. Doesn't help our mentor problem or lack there of.

[MrJohnston]

Originally Posted by Sperkowsky

Because we have no access to cnc, milling, 3d printing, 8020, or even square aluminum tubing we have to build everything out of bar stock and I bracket.

Why don't you have access to square aluminum tubing? It's really easy to order from www.onlinemetals.com and really isn't that pricey - especially if you pre-order a bunch and only pay shipping once...

[Sperkowsky]

Originally Posted by MrJohnston

Why don't you have access to square aluminum tubing? It's really easy to order from www.onlinemetals.com and really isn't that pricey - especially if you pre-order a bunch and only pay shipping once...

Well it's one of those things we never did. My mentor is pretty used to the way he's being doing things and has not been questioned much. It usually works out but whenever I mentioned in the past square of rectangular tubing he told me we couldnt use it do to lack of welding equipment. He's finally come around but not in time for this season. The thing is this year we got sponsors so stuff is going to change for next year.

[z_beeblebrox]

Originally Posted by Sperkowsky

Well it's one of those things we never did. My mentor is pretty used to the way he's being doing things and has not been questioned much. It usually works out but whenever I mentioned in the past square of rectangular tubing he told me we couldnt use it do to lack of welding equipment. He's finally come around but not in time for this season. The thing is this year we got sponsors so stuff is going to change for next year.

Aluminum tubing doesn't need welding. You can easily make good quality (strong, lightweight) aluminum tubing structures with as little as a drill, a hacksaw, tin snips and a riveter. If you have any questions on design or manufacturing best practices, you're welcome to ask here.

Back on topic, our build is a few days behind schedule, as usual. We have our robot ~90% designed, our practice robot driving and ~80% assembled, and our competition drivetrain being fabricated.

[dk5sm5luigi]

We have worked on the robot for only 4 hours in the last two weeks thanks to the many snow storms...

[Tem1514 Mentor]

So far we have lost over a week due to exams. It is real hard to tell kids forget about school and lets build a robot instead, that just will not happen.

May be FIRST should consider moving build season or making it longer.

[Bryce Paputa]

Starting to make the robot today

[Caleb Sykes]

Originally Posted by AustinH

P.S. Has anyone come up with an elegant solution to the gyro roll-over problem (going from 180 immediately to -179 or 0 to 360 and spinning in circles)?

In raw readings, the gyro should not do this, it should give continuous readings and have no rollover. Any rollover errors that you have come from the way the robot is coded. What are you trying to accomplish with the gyro?

[AustinH]

The problem comes when we attempt to use a PID loop to hold the robot at 180° relative to the field. Normal joystick rotation works just fine.

[Donut]

Base is built, just finishing up the electronics today and hoping to test it moving next meeting. Then have to get the elevator built. My biggest worry is part availability, the team has few raw materials lying around and most of the funding didn't show up until week 4. Since the PO process is slow we may not get any more parts before build ends. Most of the team is pretty upbeat, they literally showed up at the regional last year with a bare chassis and no electronics in it so for the few veterans the progress of a moving robot in week 5 is astronomical.

[Dunngeon]

We were nearly done with parts a few days ago, but our CNC mill broke.... So we are sitting still right now.

Base is done, and we're trying to figure-out how to finish the remainder of the robot.

Good luck teams, hopefully you avoid our luck!

[Caleb Sykes]

Originally Posted by AustinH

The problem comes when we attempt to use a PID loop to hold the robot at 180° relative to the field. Normal joystick rotation works just fine.

Which language are you using?

A simple solution for this specific case would be to use the following logic:
if(angle < 0)
adjusted angle = angle + 360
else
adjusted angle = angle

Then, use adjusted angle wherever you would have used angle in the rest of the code. To get it to work for the more general case, you have to be a little more creative, but you can use this same idea.