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Unread 01-08-2018, 03:59 PM
Steven Carmain Steven Carmain is offline
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Field Dimentional Accuracy

For this years game, there are very little assists to help robots position themselves for auto mode. Because of this, we were wondering how accurately field objects would be placed during field setup. (permanent ones like the scale, not the cubes)

When I look at the 2018 Field Layout and Marking rules: https://firstfrc.blob.core.windows.n...ingDiagram.pdf , it has dimensions listed that are listed to 2 decimal points, and has a warning "Unless otherwise specified, tolerances for 2 digit decimal numbers are +/-0.01", as long as the dimension is not in parenthesis. Can we really expect the FTA to get out their micrometers to measure the field to the hundredth of an inch? What is the official tolerance level for the field during an official FRC event? (I vaguely have heard that it is +/-2")

Also, if an official field line is the wrong color tape (as listed in that same manual), do the FTA's have to fix it at an official event?


(side note, I know offseason events sometimes have their own rules... like one didn't tape the auto line, and another had the airships 9" closer to driver stations, but since it was equal on both sides, they ran with it)
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Unread 01-08-2018, 04:56 PM
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Re: Field Dimentional Accuracy

Quote:
Originally Posted by Steven Carmain View Post
For this years game, there are very little assists to help robots position themselves for auto mode. Because of this, we were wondering how accurately field objects would be placed during field setup. (permanent ones like the scale, not the cubes)

When I look at the 2018 Field Layout and Marking rules: https://firstfrc.blob.core.windows.n...ingDiagram.pdf , it has dimensions listed that are listed to 2 decimal points, and has a warning "Unless otherwise specified, tolerances for 2 digit decimal numbers are +/-0.01", as long as the dimension is not in parenthesis
As per section 3 of the manual, that is the official source for tolerances. If your robot is relying on precise tolerances, please measure those dimensions during the measurement/calibration period (see 10.3 in the manual), and politely let the FTA know if anything is incorrect.

There are some dimensions that the FTA may not be able to reasonably rectify at the event. For example, if a guardrail is .02" short, the FTA will likely be unable to fix that. They may put in a call to FIRST HQ to discuss the situation though.

The biggest challenge that you are going to run into if you are relying on 0.01" tolerances is that the field undergoes changes during the course of an event. Aerial Assist was a great example- with the open field, robots would hit the alliance walls pretty hard. The field could stretch on the order of inches throughout the course of the event. Depending on the field, the FTA may or may not be able to fix that in a reasonable manner. Last year's air ships were very difficult to move. If they were significantly off from spec, an FTA may have moved the airship over night or over the lunch break, but would likely not have time to do so between matches. I expect this year's field to be similarly difficult to adjust.

Even if the FTA was to fix some of those issues before a match, it is quite likely that some elements will shift during the match. A robot running into a SWITCH at full speed is likely to shift it >= 0.01". A robustly designed robot will take relatively minor difference such as that into account.

That being said, if a field element is out of tolerance and you alert the FTA, Head Referee, or other field staff prior to the start of a match, they have a responsibility to make a reasonable effort to correct the situation.

Quote:
Originally Posted by Steven Carmain
Can we really expect the FTA to get out their micrometers to measure the field to the hundredth of an inch?
No, but you can expect them to get out the tape measure prior to the field calibration/measurement time.

Quote:
Originally Posted by Steven Carmain
What is the official tolerance level for the field during an official FRC event? (I vaguely have heard that it is +/-2")
Section 3 of the manual points to the 2018 ARCADE Layout and Marking Drawing that you linked to as the official source for tolerances.

Quote:
Originally Posted by Steven Carmain
Also, if an official field line is the wrong color tape (as listed in that same manual), do the FTA's have to fix it at an official event?
Yes. Politely alert the FTA (or Head Referee if the FTA isn't available) and they will correct the situation

One final note- know what you are and are not allowed to do when setting up for your match. In particular, check out H07, which limits the types of things you can bring to the field for a match.
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Last edited by Bryan Herbst : 01-08-2018 at 05:00 PM.
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Unread 01-08-2018, 05:48 PM
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Re: Field Dimentional Accuracy

Expect tolerances to be about 10x as bad as the rules and field diagrams say, and your competition experience will be less stressful.
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