2012 FRC Team 1717 Uncut

Wow… This surprises me. I knew of a handful of teams throughout the season who effectively used camera cross hairs. 1507, a shooter powerhouse at Finger Lakes, won the regional with those cross hairs. I believe I heard at one point 217 was using them as well, and 67 had borrowed the code for them for some time (thought this may be incorrect. Memory doesn’t serve me well nowadays).

But I never expected 1717, one of, if not the, most precise shooters in the world, would use them. This really convinces me that you don’t need complex systems to do well.

Have you looked at your driver station log files from those matches?

Not trying to hijack the thread, but I just want to clear this up. We did not use crosshairs. We just had the straight camera feed that we used to line up.

Also, this thread is just full of awesome.

Our team has done 4 wheel 360 rotation independent swerve also and loved looking at your drive at champs. Similar but different design. In the past we have used a least distance algorithm for steering. Sometimes it’s quicker to rotate a short distance and reverse the drive motor. Do you do that in your code also? This year we eliminated the motor reversal part. We still check the shortest rotation direction. The bot seams to drive much smoother this year. How did your team handle the steering algorithm?
We do not have field centric control but are looking to add the gyro this coming year. In a match on average how long did the gyro go before errors added up to the point it affected driving? How many seconds before a zeroing was needed? Did you try any digital (I2C or SPI) gyro’s or only analog?
One last question. What wheel angle sensor did you use. Do you feel it’s accuracy and resolution are good enough or do you feel high resolution is needed. How many degrees of lash does the steering have. Our bansbot gear boxes have allot of lash. We haven’t found another gear box solution that we can afford.

Leeland…you are correct. We switched to cross hair aiming at the Troy district and immediately saw a jump in our scoring numbers. It was worth approximately 2 balls/match.

Congratulations to 1717 on an incredible season. Easily the most accurate shooter this season.

Gah. Sorry again Bryan. It seems most of the things I was told about 1507’s robot were unconfirmed and not quite correct -_- I’m really sorry I keep getting the info about your robot mixed up.

Do you happen to know what part number that sensor is? I have been trying to find out what types of sensors are good but have no idea where to start looking for those sensors, let alone what ones are good/suitable for FRC.

As promised, here are several pictures of our swerve module. On this particular module, there is no turning sensor or wheel encoder, but the brackets that mount each one are present. As you can see in the photos, this module has a two speed coaxial shifting transmission for the drive and a single speed transmission to turn the modules. Nearly all of the parts were custom fabricated. All internal parts including our gears were made in our shop. The sheet metal box structure for the wheel module and transmission plates were made by one of our sponsors.
Enjoy!

http://www.chiefdelphi.com/media/img/ae1/ae18c8c13d9120ff8ebe9bd53d8c8fb0_l.jpg

http://www.chiefdelphi.com/media/img/4ff/4ff1c3a058048bdfdb2c0bd13a6d3087_l.jpg

http://www.chiefdelphi.com/media/img/47c/47c770bd83797f4e2d9fb835e1d66bd4_l.jpg

http://www.chiefdelphi.com/media/img/265/2652e2b830627a635e057ecb614b368a_l.jpg

http://www.chiefdelphi.com/media/img/c68/c68707c0934240c1d0cb3621f757dd0a_l.jpg

As promised, we have posted pictures of our wheel modules (they can be seen in recent images or you can search “1717 wheel module” on CD). On this particular module, there is no turning sensor or wheel encoder, but the brackets that mount each one are present. As you can see in the photos, this module has a two speed coaxial shifting transmission. Nearly all of the parts were custom fabricated. All internal parts including our gears were made in our shop. The sheet metal box structure for the wheel module and transmission plates were made by one of our sponsors.

To make sure everyone’s questions get answered, I would appreciate it if all of the questions are posted in this thread.

Enjoy!
Jake
FRC Team 1717

Thanks for the pics of wheel modules… sorry I missed your msg last month I sent you one recently. I’m having problems with CD notifies via email.

We are using Banebots RS-550’s for our turning transmissions. We tried to use Banebots transmissions in the past for our swerve, but found them to be too unreliable for our liking.

Our turning transmissions have now run for hundreds of hours on our practice robot and there is no visible wear on the teflon/anodized coating. They have required no service other than the initial lubrication with dry grease. Our current turning transmission gear-train weighs less than a Banebots as well. Also, the backlash is a little better than the Banebots but not by much.

Awesome.

I actually get to read “The New Cool” this summer for school!

The gears with the smaller teeth in the swerve drive, are they 32 DP? Where did you get them from (you didn’t make them yourselves did you, noticed the earlier post about gear making)? And do they come anodized or did the team anodize them themselves?

Also, for electrical, are those Anderson power connectors?

Thanks for the answer. It really sheds some light on the design of the module. On another gear question, Does your team manufacture their own bevel gears? Or do you source them from someone else?

I believe in 2011, 1717 used MC #6529K14. They of course finished the bore (hex) and cut down the face width to their needs. Not sure about this year or other years, though. They may have used something different.

The wheel module design this year was completely new. The new motor allowance for this year allowed us to build independent swerve drive without sacrificing power for other mechanisms. We designed the module during this build season as rookie seniors. It took about 2000 man hours to both design and fabricate 10 wheel modules (4 for the official robot, 4 for the practice robot, and 2 spares). The fabrication process of the modules was quite time-consuming and tedious.

On average, we seniors put in about 500 hours during the robotics season. Some of us, including the programmers and drivers, exceeded 750 hours during the robotics season. We are able to dedicate this much time to robotics because we are in our second semester with a light course load. Also, we only get one opportunity to do this awesome competition so we are extremely excited and dedicated to building our robot!

For turning, we keep track of our absolute position using a US Digital M4A. The sensor is setup 1:1 with the absolute wheel position. You can see the bent sheet metal bracket in Wheel Module Picture 3 to the front left.

For the drive, we are using an optical encoder that is attached to a small aluminum shaft. This shaft is directly coupled to the CIM motor and therefore one-to-one with the speed of the CIM. It keeps track of wheel rotations. You can see the flat mounting plate in Wheel Module Picture 4 right next to my thumb.

Sorry about resurrecting an old thread (albeit an awesome thread), but I’ve been thinking about the accuracy of this shooter for the past week. Aside from the crosshairs and software put into shooting, what mechanical advantages did it have? Like what mechanically did they do to their shooter along with the code to make it so darn accurate?

Jake, (or anyone else for that matter)
I have a question about swerve drive… is it common to allow some degree of freedom of being able to align the wheels perfectly straight if you want to go straight? It seems like if you tighten your grip too much you may run into oscillation. Assuming there is some tolerance what would be a good metric for this (I think I remember reading 2 or 3 degrees somewhere elsewhere in the forum).

The pulleys are made from pulley stock purchased from Stock Drive. The clamp is a custom machined part that clamps onto a specially designed custom cut pulley that originally came from a length of pulley stock.

Sorry for the late responses. Thanks for all of your interest in our robot!