Mechanum Problems...

[Must Be Drama]

we totally forgot how to set up mechanum.. we used the holonomic drive and set x to rotate but it doesnt do anything

[Ether]

Originally Posted by Must Be Drama

we totally forgot how to set up mechanum.. we used the holonomic drive and set x to rotate but it doesnt do anything

First, since it's so easy to check, and it affects the ability of mecanum (no "h") to rotate, make sure that the wheels are mounted properly.

If that checks out OK, load the default 4-motor tank drive code that came with the Framework. Put the vehicle up on blocks and verify that the motors are spinning in the right direction.

If that checks out, post your code for review.

[Carter12s]

Last years mecanum code was slightly more advanced than this years. Last years code allowed for a scaled (X,Y) cartisian input. This year the mecanum drive requires a direction and magnitude vector to operate. Some simple geometry (A^2 + B^2 = C^2) can get you back to that system, but you need to provide a direction and magnitude for the the new mecanum version to operate.

[bladetech932]

Cartesian is still in the holonomic vi nothings changed

[Dfontana]

I can vaguely remember doing this last year for team 3039's robot which implemented mechanum wheels.

Prior to one of the LabView Updates about midway through the 2010 season, there was no specific "complete" VI for this drive system. Since we decided we also wished to use a gyrometer, we spent the better part of a week manually coding in the required variables to the already existing holonomic VI, only to be given the completely encapsulated one the next week. Bummer.

Anyway, the experience gave us a little insight into how the system actually worked. As mentioned above, cartesian coordinates were essential to our implementation.

Consider the unit circle covered in most high school pre-calc classes applied to a joystick controller. The length of the radius (distance of the joystick from its neutral position) would be your magnitude, calculated with pythagorean's theorem. The direction, then, would be the theta angle, calculated by finding the tangent of x/y. All these math functions were and are available in labview.


The new VI, however, did not require you to do this. You simply feed it the x and y-axis values from a particular joystick, along with a third axis (from either the same joystick - throttle - or a second joystick) for rotation. It then does all calculations for you. In the event that you wish to use a gyrometer, as we did, for field-oriented control, simply wire in the gyro angle to its corresponding input on the Holonomic VI.

Please note that all of this information is based on personal knowledge of LAST YEARS holonomic VIs. It may or may not apply to this years.

Hope this helps.

[Ether]

Originally Posted by Dfontana

calculated by finding the tangent of x/y

I assume you meant the arctangent.