Holonmic VI not Working Properly Mechanum Drive

[MartinB]

I was testing out the homonymic VI on the mechanum wheels we have and when I was telling it to strafe (I am using Cartesian mode, so that means sending a value to X) it was rotating and when I was trying to rotate, it strafed. Forward and backwards works, but the unexpected behavior is a little weird. Has there been any changes to the VI behind the scenes that would cause this? Thank you in advance for information.

[Greg McKaskle]

It sounds a bit like the axes from the joystick are flipped. Can you probe them, or isolate them to determine if that is the problem?

Greg McKaskle

[Ether]

Originally Posted by Greg McKaskle

It sounds a bit like the axes from the joystick are flipped. Can you probe them, or isolate them to determine if that is the problem?

Greg McKaskle

I think he has the vi wired incorrectly, but I don't have LabVIEW installed here so I can't check it.

See the first JPG attachment to this post.

[MartinB]

I blame the joystick, its wired backwards because the joystick sends a -1 when its pushed foward and a 1 when its pushed backwards. So in testing it this way by sight, fowards should have been backwards on the joystick because of these mixed signals. Thanks for your help.

[Greg McKaskle]

It isn't the joystick, it is HID. They define forward as negative. My guess is that they were thinking airplane flight stick ... It is just a convention anyway.

Greg McKaskle

[Alan Anderson]

Originally Posted by MartinB

So in testing it this way by sight, fowards should have been backwards on the joystick because of these mixed signals. Thanks for your help.

The Cartesian Mecanum Drive vi helpfully accounts for the "negative is forward" convention of a joystick.

[MartinB]

I wasn't paying much thought towards the motors when I was designing the diagrams to think I was switching the motors. I'll test out completely switching the true and falses when I get to test again.

Edit:
Got it working, here is a link to see the resulting change on our test bed http://www.youtube.com/watch?v=mhM_RQoiQXY
I still need to some more coding to iron out some of the problems, but I think I am doing well considering I am the only team member using labview and programming for autonomyous.

[Alan Anderson]

Originally Posted by MartinB

...when I was telling it to strafe (I am using Cartesian mode, so that means sending a value to X) it was rotating and when I was trying to rotate, it strafed. Forward and backwards works, but the unexpected behavior is a little weird.

This might happen if you have your left and right motors swapped at one end. make absolutely certain that what you're telling the Open Four Motor Drive matches the reality of your robot.