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 Chief Delphi Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs
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#31
09-12-2017, 10:21 PM
 SuperMario210 Registered User FRC #0254 (The Cheesy Poofs) Team Role: Programmer Join Date: Sep 2017 Rookie Year: 2015 Location: San Jose Posts: 7
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by buildmaster5000 One question I have reading through the binder (which is amazing!): How did you develop your function to correlate shooter wheel speed to a function of distance, and how did you measure the distance?
To create our distance to shooter RPM function, we first collected a set of distance to RPM data points by fixing our shooter RPM to various values and finding the optimal distance for each RPM. We then used a quadratic polynomial regression to find the best fit function for these data points.

The general idea behind finding distance to the boiler is to find the vertical angle to the boiler then use trig/similar triangles to calculate distance from this angle. First we calculate the vertical angle between our camera and the vision tape using this equation: atan(y_pixel_position / focal_length) where a (0,0) pixel position is at the center of the screen. Once we have the vertical angle to the target we use some basic trig to calculate the distance to the boiler ( range = cot(vertical_angle) * height_difference where height_difference is the height difference between the camera and the boiler). We gave an in depth explanation about it at the Integrating Computer Vision with Motion Control presentation at the 2016 FIRST Championship.
#32
09-12-2017, 10:29 PM
 dardeshna Team Captain AKA: Devin Ardeshna FRC #0008 (Paly Robotics | Team 8) Team Role: Mechanical Join Date: Dec 2015 Rookie Year: 2015 Location: Palo Alto Posts: 105
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by buildmaster5000 One question I have reading through the binder (which is amazing!): How did you develop your function to correlate shooter wheel speed to a function of distance, and how did you measure the distance?
Quote:
 Originally Posted by TylerHarmon I'm not on 254, but according to the tech. binder: "An Interpolating Tree Map determines the correct flywheel RPM for the current distance"
I believe an Interpolating Tree Map is basically linear interpolation between several calibrated values.

Linear interpolation: Imagine a set of plotted points, then draw lines to connect them instead of fitting a curve to the data.
__________________
Devin Ardeshna
Team Captain (Paly Robotics FRC #8)

2017 Ventura Regional Quarterfinalist, Entrepreneurship Award, and Creativity Award, Silicon Valley Regional Finalist, Entrepreneurship Award, and Wildcard, Roebling Division Semifinalist
2016 Central Valley Regional Finalist and Wildcard, Silicon Valley Regional Quarterfinalist, Curie Division, CalGames Quarterfinalist and Entrepreneurship Award, Capital City Classic Quarterfinalist
2015 Central Valley Regional Entrepreneurship Award, Silicon Valley Regional Entrepreneurship Award, Capital City Classic Semifinalist and Judges' Award
#33
09-12-2017, 11:16 PM
 davispitts3577 Registered User FRC #3577 (Saints Robotics) Team Role: Electrical Join Date: Aug 2017 Rookie Year: 2017 Location: Arizona Posts: 24
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by Ashwin254Adulla To calculate the angle of the hood, we took into account where in the field we wanted to shoot from (front hopper during autonomous), where the hood would be vertically placed on the robot, and at approximately what angle we wanted the ball stream to enter the boiler. For SFR and SVR, our first iteration of the hood had a fairly shallow angle (around 20 degrees above the horizontal) which led to a non-optimal trajectory which gave us an accuracy of roughly 60-70% at these two regionals. For Champs, our priority was changing the hood to a) have less compression and b) reduce the angle to give us a better trajectory. To test out which angle we wanted, we went through a series of iterations consisting of placing blocks below the front of the robot to effectively decrease the exit angle of the balls and then translating that new effective angle into a CAD hood prototype which we laser cut and mounted in place of our current hood. We ran through around 5 iterations to get to our final hood angle of 14 degrees.
Just sent you a PM.
#34
09-13-2017, 03:42 AM
 Cory Registered User AKA: Cory McBride FRC #0254 (The Cheesy Poofs) Team Role: Engineer Join Date: May 2002 Rookie Year: 2001 Location: Redwood City, CA Posts: 6,948
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by juju_beans Not 254, but my team also used #25 chain for our drive train without tensioners. We used the the exact c-c length + 3 thou, which we found using this calculator. Over the season the chain did start to loosen up and sag a tiny bit, but since we used chain-in-tube, the chain wouldn't be able to fall off. As for how long they lasted, both our practice and our competition bot still have their original chains. For machining tolerances, they really weren't anything special especially since all of my team's metal working is done on a cheap mini mill with a DRO.
.003 is nowhere near enough in our experience. Paul Copioli has a tool somewhere (I think in a presentation he made) that we used as a starting point and then did empirical testing of additional added distance.

We used +.018" on a 10.75" C-C run (very close, if not exactly what Paul recommended) and +.030" on a 20.75" C-C run.
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2001-2004: Team 100
2006-Present: Team 254
#35
09-13-2017, 09:38 AM
 Ty Tremblay Robotics Engineer FRC #0319 (Big Bad Bob) Team Role: Mentor Join Date: Feb 2006 Rookie Year: 2004 Location: Alton NH Posts: 945
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by Cory .003 is nowhere near enough in our experience. Paul Copioli has a tool somewhere (I think in a presentation he made) that we used as a starting point and then did empirical testing of additional added distance. We used +.018" on a 10.75" C-C run (very close, if not exactly what Paul recommended) and +.030" on a 20.75" C-C run.
I'll second the empirical approach. We found that chains from different manufacturers will require different additional c-c for the same run. (Vex heavy duty #25 vs McMaster #25 for example).
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#36
09-13-2017, 09:42 AM
 Nate Laverdure Cynicism isn't wisdom FRC #2363 Team Role: Coach Join Date: Apr 2005 Rookie Year: 1999 Location: Newport News, VA Posts: 910
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by Ty Tremblay I'll second the empirical approach. We found that chains from different manufacturers will require different additional c-c for the same run. (Vex heavy duty #25 vs McMaster #25 for example).
Thirded. We found that even chain from the same vendor, but purchased at different times, will require different additional c-c for the same run.
#37
09-13-2017, 10:07 AM
 Cothron Theiss Registered Muser FRC #4462 (Full Metal Jackets) Team Role: College Student Join Date: Feb 2016 Rookie Year: 2013 Location: Kingston, Tennessee Posts: 799
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by Cory .003 is nowhere near enough in our experience. Paul Copioli has a tool somewhere (I think in a presentation he made) that we used as a starting point and then did empirical testing of additional added distance. We used +.018" on a 10.75" C-C run (very close, if not exactly what Paul recommended) and +.030" on a 20.75" C-C run.
Quote:
 Originally Posted by Ty Tremblay I'll second the empirical approach. We found that chains from different manufacturers will require different additional c-c for the same run. (Vex heavy duty #25 vs McMaster #25 for example).
Quote:
 Originally Posted by Nate Laverdure Thirded. We found that even chain from the same vendor, but purchased at different times, will require different additional c-c for the same run.
Mind sharing your teams' methods of empirically determining addendum distance? It's a bit of a tangent and possibly deserving of its own thread, but I'd appreciate a quick run through.
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#38
09-13-2017, 10:20 AM
 Nate Laverdure Cynicism isn't wisdom FRC #2363 Team Role: Coach Join Date: Apr 2005 Rookie Year: 1999 Location: Newport News, VA Posts: 910
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by Cothron Theiss Mind sharing your teams' methods of empirically determining addendum distance? It's a bit of a tangent and possibly deserving of its own thread, but I'd appreciate a quick run through.
Here you go!
Quote:
 Originally Posted by ToddF This summer we are experimenting with non-adjustable wheel positions, and chains inside our side rails. The first rail we made had nominal C2C distances. While it is functional, the chains sag enough to touch the inside of the rail tube, making the drive assembly noisy when running. For the second tube, we took a WAG (embarrassing to admit, for engineers), and increased the C2C distance about .008". This resulted in saggy chains again. After that, we did what we should have done from the start, and actually measured the C2C distance of tensioned chains, instead of just guessing. We made this test setup, first using the chain from our experimental drive train, with a nominal C2C distance of 10.75". Note that the sprockets, bearings and shafting are all 1/2" hex type, all from VEXpro. There are slip fit tolerances between these parts that require the C2C distance of the bearing pockets to be greater than nominal to achieve a tight chain. Also note that the neither the hex holes in the bearings nor the hex holes in the sprockets are truly concentric. This leads to visible wobble in the OD of the sprockets, when they spin. This causes the chain tension to vary, and is a source of vibration and cyclic fatigue to the overall drivetrain. To test whether any C2C variations were related to the length of the chain, we also tested a nominal 4" C2C chain setup. The chain tension was set by anchoring one of the bearing blocks, pulling the chain "finger tight" and locking down the other bearing block. We then spun the chain by hand to observe that it could run free, and hand checked the chain tension the same way we do in the pits, to be sure it was tensioned comparably to our competition drive trains. Then we removed the chains, sprockets, shafts, and upper bearings. The upper bearings have a tight slip fit. To remove them, it was necessary to insert the end of an axle shaft and wiggle it around, working the bearing loose. This left the two bearing blocks with the bearing pockets exposed. We then used the milling machine edge finder and the dimensional readout to find the C2C distances (we actually measured to the left sides of both bearing pockets). Here are the results: We concluded that the increase in C2C distance was due to the tolerance stackup of the parts, and not tightly related to the length of the chains. We plan to incorporate a .019" to .020" delta to our nominal C2C distances in future designs.
#39
09-13-2017, 10:37 AM
 JesseK Expert Flybot Crasher FRC #1885 (ILITE) Team Role: Mentor Join Date: Mar 2007 Rookie Year: 2005 Location: Reston, VA Posts: 3,955
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

I heard from a student at WCMP that current draw while shooting was a large concern. How bad was it, and what adjustments were made?

What, if any, fine-tuning needed to be made after importing from the Cheesy-path app? During refinement, was the default strategy to re-tune the path in the app, or re-calibrate sensors (etc) to get the actual path to match the desired path? What margin of precision was "good enough" for the gear + hopper auton?

Edit - Also, was it seen as a risk that a drive train CIM would be hit, given how close (or over?) the edge of the angled frame it is?
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2017: Scoring Model | COPR Rank Simulator

Last edited by JesseK : 09-13-2017 at 10:41 AM.
#40
09-13-2017, 11:50 AM
 Ty Tremblay Robotics Engineer FRC #0319 (Big Bad Bob) Team Role: Mentor Join Date: Feb 2006 Rookie Year: 2004 Location: Alton NH Posts: 945
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by Cothron Theiss Mind sharing your teams' methods of empirically determining addendum distance? It's a bit of a tangent and possibly deserving of its own thread, but I'd appreciate a quick run through.
Quote:
 Originally Posted by Nate Laverdure Here you go!
Ours is a modified method from 2363's post above. We milled the bearing holes in a 2x1 tube, then cut the tube in the middle. Then we assembled the chain on, pulled the two pieces apart, tightened the vice, and measured.

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#41
09-13-2017, 01:14 PM
 Cory Registered User AKA: Cory McBride FRC #0254 (The Cheesy Poofs) Team Role: Engineer Join Date: May 2002 Rookie Year: 2001 Location: Redwood City, CA Posts: 6,948
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by Cothron Theiss Mind sharing your teams' methods of empirically determining addendum distance? It's a bit of a tangent and possibly deserving of its own thread, but I'd appreciate a quick run through.
Nothing fancy here. Machined test rails with bearing bores at .005" increments and picked the one that felt best.
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2001-2004: Team 100
2006-Present: Team 254
#42
09-13-2017, 01:50 PM
 Rafi Ahmed Mentor & Alumni FRC #2522 (Royal Robotics) Team Role: Mentor Join Date: Mar 2005 Rookie Year: 2002 Location: Seattle Posts: 204
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by Cory Nothing fancy here. Machined test rails with bearing bores at .005" increments and picked the one that felt best.
Was 25 chain used? Did you have any chain skipping or had to swap it out in the middle of the season?
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Team 2522 | Mentor
Formerly of Team 22 and Team 4
#43
09-13-2017, 02:39 PM
 Cory Registered User AKA: Cory McBride FRC #0254 (The Cheesy Poofs) Team Role: Engineer Join Date: May 2002 Rookie Year: 2001 Location: Redwood City, CA Posts: 6,948
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by Rafi Ahmed Was 25 chain used? Did you have any chain skipping or had to swap it out in the middle of the season?
#25 chain, no issues.
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2001-2004: Team 100
2006-Present: Team 254
#44
09-13-2017, 04:47 PM
 Lil' Lavery TSIMFD AKA: Sean Lavery FRC #1712 (DAWGMA) Team Role: Mentor Join Date: Nov 2003 Rookie Year: 2003 Location: Philadelphia, PA Posts: 7,044
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Was the initial effort of empirically determining C-C distance for individual chain runs worth it compared to adding some sort of adjustable tensioning device?
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#45
09-13-2017, 05:33 PM
 Cory Registered User AKA: Cory McBride FRC #0254 (The Cheesy Poofs) Team Role: Engineer Join Date: May 2002 Rookie Year: 2001 Location: Redwood City, CA Posts: 6,948
Re: Team 254 Presents: 2017 Misfire Technical Binder and Build Blogs

Quote:
 Originally Posted by Lil' Lavery Was the initial effort of empirically determining C-C distance for individual chain runs worth it compared to adding some sort of adjustable tensioning device?
It was 20 minutes of CAM/CNC time and saved us making 3 days worth of parts, so 100% worth it.
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2001-2004: Team 100
2006-Present: Team 254

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