how to program mecanum wheel drive?

[sonicwingmode]

what do we put in the rotation?

[Owen Meaker]

Originally Posted by sonicwingmode

what do we put in the rotation?

rotation is the, well, rotation of the robot. If you have a joystick that can be twisted, you can use that (for our joystick its axis 4, but it could be different for other joysticks). If your joystick does not support twisting, you will need to have buttons that are wired in (for example, put in a case structure that determines which button is being pressed, that then outputs a 1 or -1 depending on which way you want to rotate it).

[kornjones]

My team has been using mecanums for a few years and at the beginning of the year an alumni asked me to make a program that could take full advantage of the mecanum wheels instead of our usual tank drive with trigger strafe boringness. after much thought and many matrices i realized that if you subtract the y axis form the x axis for the front right and back left and add y and x axes for the front right and back left we could make what i like to call omnidrive. it basically made it so that the robot would move in any direction the stick was pointing. after some more finagling i put the controls on two sticks and fixed a few value issues and now we have 2 stick mecanum omnidrive. its pretty difficult to explain but its fantastic to drive. if anyone needs any help i am also available for assistance

[Ether]

Originally Posted by kornjones

My team has been using mecanums for a few years and at the beginning of the year an alumni asked me to make a program that could take full advantage of the mecanum wheels instead of our usual tank drive with trigger strafe boringness. after much thought and many matrices i realized that if you subtract the y axis form the x axis for the front right and back left and add y and x axes for the front right and back left we could make what i like to call omnidrive. it basically made it so that the robot would move in any direction the stick was pointing. after some more finagling i put the controls on two sticks and fixed a few value issues and now we have 2 stick mecanum omnidrive. its pretty difficult to explain but its fantastic to drive. if anyone needs any help i am also available for assistance

What you have described has no rotation. Perhaps you left something out of your description?

Also, I assume there's a typo in there, because you said "front right and back left" twice.

[sjspry]

That picture should make it fairly obvious. If not, look below. mainJoy is the one used for forward/back and strafing, rotJoy is used for rotation (pretty much like a FPS game, we even wired our camera's tilt up to rotJoy's Y axis so it is exactly like the usual FPS controls ) For best results, use an Xbox/PS3 controller. Remember forward is -1.

Assuming you get -1..1:

front_Left = -mainJoy.getY() - rotJoy.getX() + mainJoy.getX()
front_Right = -mainJoy.getY() + rotJoy.getX() - mainJoy.getX()

back_Left = -mainJoy.getY() - rotJoy.getX() - mainJoy.getX()
back_Right = -mainJoy.getY() + rotJoy.getX() + mainJoy.getX()

[Ether]

Originally Posted by sjspry

mainJoy is the one used for forward/back and strafing, rotJoy is used for rotation... Remember forward is -1.

front_Left = -mainJoy.getY() - rotJoy.getX() + mainJoy.getX()
front_Right = -mainJoy.getY() + rotJoy.getX() - mainJoy.getX()

back_Left = -mainJoy.getY() - rotJoy.getX() - mainJoy.getX()
back_Right = -mainJoy.getY() + rotJoy.getX() + mainJoy.getX()

Two suggestions:

1) I would think it would be more intuitive if pushing rotJoy to the right would cause clockwise rotation*.

2) You need to normalize the 4 wheel commands, in a way that preserves their holonomic relationship, before sending them to the motors.


* I am assuming that the motors are set up so that issuing a + command causes the wheels to rotate in the "forward" direction

[sjspry]

Originally Posted by Ether

Two suggestions:

1) I would think it would be more intuitive if pushing rotJoy to the right would cause clockwise rotation*.

2) You need to normalize the 4 wheel commands, in a way that preserves their holonomic relationship, before sending them to the motors.


* I am assuming that the motors are set up so that issuing a + command causes the wheels to rotate in the "forward" direction

As for #1, yeah, as far as I know everything should be backwards because of the Joystick output. They might need to modify it....

Didn't know about the handy PDF, though. Thanks

[Ether]

Originally Posted by sjspry

As for #1, yeah, as far as I know everything should be backwards because of the Joystick output. They might need to modify it....

The joystick X-axis is + to the right. So your code should be

front_Left = -mainJoy.getY() + rotJoy.getX() + mainJoy.getX()
front_Right = -mainJoy.getY() - rotJoy.getX() - mainJoy.getX()

back_Left = -mainJoy.getY() + rotJoy.getX() - mainJoy.getX()
back_Right = -mainJoy.getY() - rotJoy.getX() + mainJoy.getX()

[sonicwingmode]

so, how do I program this?

[Ether]

Originally Posted by sonicwingmode

so, how do I program this?

Just like any other motor: it depends on what you want to do with it.

[sonicwingmode]

ok, thanks

[sonicwingmode]

our team is trying to use the relay to control the window motor, how do we program this?