paper: FRC1477 2013 Robot CAD Files

[James Tonthat]

Originally Posted by btslaser

Very nice, thanks for posting this. Couple questions...

1) It looks like there are 2 different types of encoders on the shooter pitch angle. Is this just for redundancy? If so, why two different types?

2) What type of machinery do you have access to? Manual mills/lathes, CNC milling, laser sheet metal, etc.

1. We were playing around with using incremental encoders for differential output so we could do motion profiling (with a US Digital S4), what we ended up using is the US Digital MA3 encoder which gives an analog output (0-5v). We had originally used the MA3 directly on the tilt shaft but that would only give us 1:1 resolution on the angle of the shooter. We ran it back through a 14T to give us 5.14 times the resolution so noise on the analog breakout would appear "smaller". This basically allowed us to use about 85% of the sensor's rotation and resolution to give us better readings. Also, I just realized the "shooter tilt" doesn't reflect what was on the robot. It's simply a BAG Motor, 100:1 Versaplantery, 14T spur gear to a 72T mounted to the holes there and the motor is mounted to the holes there, that "kit" with the two extra 14T's on the Versaplanetary don't exist in real life.

2. It varies from year to year. This year we primarily relied on CNC milling, all the 0.25" plate and tubing you see was done on Team Kaos 1429's mill that they graciously let us use. The 0.090" and 0.125" aluminum sheetmetal was done at Innovation First's sheetmetal shop, all of it was designed to be CNC punchable. In our shop, we have a small hobby lathe that we can turn out small parts that don't necessarily need a lot of precision. At UT-Austin, I do the more precision lathe parts on a collet lathe with a 5C 1/2 hex collet at a machine shop there. Also in house, we have a CNC router (that we mainly do plastics on) with about a 18"x18" work envelope and a small (tiny) CNC lathe that we can do small metal parts on. We have fantastic sponsors that allow us to build the way we do but every year we're flexible on design techniques and resources to make sure we're best utilizing all our resources.