We’ve started working on odometry for our swerve bot, and we found out that due to the carpet’s weave, we measure ~5% more distance when driving in a certain direction. For example, we drive 100cm, but the robot would report 105cm.
Do we know the orientation that the carpet will have on the field? And is it consistent for both halves of the field?
The carpet comes off two rolls, with the roll’s extension going from one alliance station to the other.
Every field setup I’ve ever done* here in the States had the carpet coming out of the same end of the field when unrolled, so it should be consistent in that regard–but I don’t know if there’s anything different that happens with the carpets at events in Israel.
If it’s that mission-critical, I might suggest planning a way to collect data during a practice match at the event so you can tune constants.
If you look at the Layout and Marking Diagram from the Field Drawings, you can see the two carpet pieces as long rectangles under the field, with the seam between them going lengthwise and going under the centers of the alliance stations.
Now, if you’re asking if the carpet is laid down and unrolled from the red side toward the blue, or from the blue side toward the red, I wouldn’t expect that it would be consistent from event to event.
You may get some performance improvement by switching to roughtop tread; the interlocking effect of the tread texture helps negate this issue which is one of the things that plagues molded polyurethane wheels like Colsons and higrips.
If you are sticking with Colsons, some have reported improvement in this by adding siping cuts to the wheels, your mileage may quite literally vary here.
I’m on the same team as @Yonatan8070.
We are using the roughtop tread (sds mk4 swerve) and we are planning to switch to the Mc master carr 3ply black tread, will we see any improvement?
Top 10 ChiefDelphi robot puns of all time. Prove me wrong.
I’m a little surprised you’re seeing what you’re seeing then, the blue roughtop used on those treads is the gold standard. Are you at full weight already? And how do you attach the tread? Maybe you are robbing yourself of traction in some way.
Every team I’ve heard of or worked with that ran into this carpet grain encoder slip issue had some other kind of wheel and near-instantly fixed it switching to roughtop.
This is not true, we still see it on our swerve drive to this day. All roughtop did was make the issue less severe.
Might look into making the WPILib odometry classes able to compensate for this in the future.
As others have said. The carpet come as two 15 wide rolls. The carpet machine direction is always the long field direction. The cross machine direction is the short width of the field. Other than that it is completely random. I do not know of a specific rule that specifies the weave direction so if they were to do something like patch a big hole, the weave direction might be completely different.
Carpet nap is not guaranteed to be a consistant direction… We actually talked to carpet manufactureing engineers and it’s a long story on what causes the phenomena but it can change mid roll so I don’t think it can be characterized or regulated.
It’s surprising that you’re seeing that much with roughtop. Good to know it can still be an issue.
New SysID mode to generate a vector field of the carpet nap?
Can you point me in the direction of this black tread?
In general the nap does run in the same direction for both rolls, though as Mark pointed out that may not always be consistent.
In general the carpet is unrolled in the same direction and in most cases it will be starting at the end closest to the door it entered the room at. Whether that is the red side or the blue side is going to depend on the venue.
Careful, there are many types of black roughtop that vary by what is laminated together. If you get the right stuff it is gold, but if not… YMMV.
Do you have any insight on the differences between the Neoprene and the SBR roughtop options from McMaster, and which one would be better suited to use in FRC?
Oh geez… @Mark_Wasserman ? You got the details?
Not on Neoprene. Nitrile isn’t neoprene right?
We’ve used both from mcmaster, both work, both wear way faster then Nitrile, if you go with SBR expect to change it at least once every competition it’s both thinner and softer then the Neoprene (2ply vs 3ply), and the Neoprene is softer and wears quicker then Nitrile, you can make it through 1 competition without needing to change it out, but will most likely need to before your third event if not before playoffs for your second. Also your mileage will vary depending on wheel width, type of drive train and how hard you play.