4 motor Mecanum wheel code request

[furiousgeorge]

Originally Posted by daltore

There is a Holonomic.vi in the WPIlib LabView files (should be under RobotDrive?). This VI takes 4 required inputs:

1) RobotDrive data cluster
2) Magnitude - Requires a value from -1 to 1. If you're using one joystick for strafing, this will be Pythgorean theorem (sqrt(Xaxis^2 + Yaxis^2)).
3) Direction - Requires a value from -180 to 180 (degrees). If you're using one joystick for strafing, this will be the Arctan2 between the two joysticks (found under Mathematics>Elementary>Trigonometric, it should be the last VI). Plug in the Y axis to Y and the X axis to X. This returns a value in radians, so you have to convert to degrees by dividing by Pi (Numeric>Constants>Pi) and multiplying by 180.
4) Rotation - Requires a value from -1 to 1. You can use the X axis of a second joystick, the rotation axis from a 3-axis joystick, or anything else that's convenient.

You can actually split the duties up between joysticks so you have forward/backward on one joystick and strafing on another joystick, and it will still work perfectly, just run the wires correctly. Our Girl Scouts team last year used this VI and to rotate, used the left and right buttons on top of one of the joysticks (full rotate left or full rotate right). We're using a 3-axis joystick this year that controls all of the driving. To rotate, you have to push the trigger, and to rotate with more control, you can push the button under the thumb, and it squares the value being sent to Rotate (all of the strafing still works, we just didn't want to accidentally rotate because the Z axis is so sensitive).

Hope this helps. If you were planning on using a different setup (like what Alan said with the tank steering with strafing) let us know and someone will be able to help you with that. This is just one way.

I am actually interested in finding out how to program our team's mecanum wheels so that we can have a tank drive style steering with strafing. This is our second year of FRC and so I know some of the lingo of LabView, but pictures help a lot. Thanks

[Ether]

Originally Posted by furiousgeorge

I am actually interested in finding out how to program our team's mecanum wheels so that we can have a tank drive style steering with strafing.

The following post might be of interest to you:

http://www.chiefdelphi.com/forums/sh...383#post916383


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[eovnu87435ds]

Ether's Post was a lifesaver for holonomic drive(partly because it is so easy to make sense of.) I whipped this up after reading it. All you need to do is plug in your joystick dev ref to the one side, and then plug the 4 values that output on the right into your 4 drive VI's.

Download it here: http://files.me.com/eovnu87435ds/k0i3pn
(Link expires March 19, 2010)

Note, I did not test this yet, since we didn't get our mechanum wheels yet

hope this helps, and of course, all credit goes to Ether

[Ether]

Originally Posted by eovnu87435ds

I did not test this yet, since we didn't get our mechanum wheels yet

When you get your wheels, make sure you mount them properly:


http://www.chiefdelphi.com/forums/sh...d.php?p=907174

http://www.chiefdelphi.com/forums/sh...d.php?p=907168



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[inventor1254]

Sorry I've been pretty busy I have 4 college classes to keep up with too.

I talked with our machine tool instructor and he explained a little better what we need, and to answer Alan Anderson's question way back, we need Tank drive plus strafe, 2 joysticks both controlling one side of the robot on the y for tank drive and one or both as strafe on the x. He is going to have some more students look for code through emailing people on youtube.

Again sorry I haven't been keeping up on this thread vary well, our tech center has 8th grade visits right now, so I wasn't even any where near the robot to try any of this code all week, nor am I now, and I won't be until Tuesday (Feb 23)

Again thanks for all the help the! The pdf that Ether posted http://lib.store.yahoo.net/lib/yhst-...lSpecSheet.pdf has has defiantly cleared a few things up for me, and the code http://files.me.com/eovnu87435ds/k0i3pn looks interesting, will try it when If I ever get my hands on the robot before the deadline lol.

[Alan Anderson]

Originally Posted by inventor1254

...we need Tank drive plus strafe, 2 joysticks both controlling one side of the robot on the y for tank drive and one or both as strafe on the x.

That's very easy to do using the "Mecanum - Cartesian" vi. Use the average of the joysticks' X values as the X input, the average of the joysticks' Y values as the Y input, and the difference between the Y values (divided by 2) as the rotation input.

[inventor1254]

Originally Posted by Alan Anderson
That's very easy to do using the "Mecanum - Cartesian" vi. Use the average of the joysticks' X values as the X input, the average of the joysticks' Y values as the Y input, and the difference between the Y values (divided by 2) as the rotation input.

"Mecanum - Cartesian" vi, is that in the example files? I don't know because I still don't have direct access to them, just a basic evaluation copy of LabView on my laptop.

Is there any where I can download those example files onto my computer so I don't have to be at the school?

Thanks to all the help again!

[Alan Anderson]

You can use the disks from the Kit of Parts to load LabVIEW for FRC on your own computer. Then download and install the LabVIEW update (see http://www.usfirst.org/frccontrolsystem for the link).

The HolonomicDrive vi is in the RobotDrive palette of the WPI Robotics Library functions. Once placed on the block diagram, it can be changed from Polar to Cartesian input.

[smcmahon]

Alan- is this sort of what you were talking about?

I guess I should note that Axis 3 and Axis 4 are a second set of X+Y axis from our Logitech Dual-Action Gamepad

[Alan Anderson]

Originally Posted by smcmahon

Alan- is this sort of what you were talking about?

That looks exactly like what I was talking about.