I can’t seem to find any documentation on how to do field centric meca wheel coding. Does anyone know where to find some documentation.
Sorry, are you referring to absolute position tracking on mecanum wheels or something else?
no, field centric is when the robot goes straight based off of the driver and not based off of the front of the robot.
Ah. Team 224X had a field centric X drive in SS, maybe hit them up on the forums or discord? The logic probably generalizes pretty well.
You need to know your robot’s angle, and then based on that you add the vector (magnitude is sqrt((joystick x axis)^2 + (joystick y axis)^2) and angle is atan(joystick y axis / joystick x axis)) of the joystick to the robot.
Implementation wise, that entails applying the x component of the vector between robot’s heading and the desired heading in the “strafing” direction and subtract the y component, the “forward” direction for each wheel.
The math is pretty much what @M8R said.
The hardest part, however, is for the robot to estimate and maintain the accurate true “North” heading. There is gyro drift, wheels’ slippage, and other sources of estimation errors…
We tried to do this for NbN. For debugging purposes and to let drivers know what robot thinks of its current heading there was a motor mounted on top of the robot with a giant cardboard arrow to indicate the heading. Then drivers could turn their own body to align with arrow or use special controller keys to adjust the robot’s heading estimate.
As you can imagine this wasn’t something that makes drivers’ life easier. It was more confusing than helpful and cost extra motor. So it was scrapped after less than a week of testing.
In any case, here is some useful related information:
Yeah, as @Anomaly said, we had one in SS and NBN, hit me up if u want help
Tell all of us, please?
sadly, the solution(?) listed in the last post:
is a broken link. @jpearman, can you recover this?
For more fun:
Field vs Robot Centric
@rhowbot Thanks to the way back machine, the information is not lost! I was able to track the info back to this post from @jpearman
Anyway, I wouldn’t recommend using it. Like some others have said it is not user friendly, and does not in any way make it easier and more efficient to drive. If anything it is just cool, but not practical in competition. Hope this was of help!
Impressive, what search term, what method do you use to get wayback to deliver this?
@224x how did it work for you?
@rhowbot I simply put the broken link in the wayback machine and it miraculously had indexed the page. I copied a portion from the post and searched for it on the vex forum which brought me to the original post I had linked to several years back.
Good. That will work when there is a link and it is indexed.
This one from that thread, I deleted the trailing " on the post number:
onmi directional motion
And Holonomic drives 2.0: A video tutorial by Cody required a Google search.
I would correct the thread title spelling, but we cannot anymore…
I had two gyros, so it’s harder to drift, and then all you have to do is make “forwards” change as the gyro value changes, if you do this you have a field centric homologous drive and it’s quite easy to tweak values. Judges love it
The two gyros mean that you can callebrate them to rely on each other so they don’t drift as much, it’s hard too explain. It’s basically checking them against each other to minimize drift, the fact that your only using gyros also means there’s no wheel slip, we also had a button that would recalibrate them if they got too off, all you do is face the bot away from you and reset the gyros