how to program mecanum wheel drive?

[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?

[Ether]

Originally Posted by sonicwingmode

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

http://www.chiefdelphi.com/forums/sh...09#post1025209

[sonicwingmode]

edit: where do we put the program in?