Mechanum Problems...

[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.