Mecanum drive problems

[mattom1992]

We have been programming our robot in regards to driving, but are having problems getting all of our expected results. We are programming with the holonomic.vi and are controlling the robot with a 3-axis Logitech Extreme 3D Pro Joystick. As of right now, we are able to move forward, backwards, left, right, and in both a CW and CCW rotation. Our problems come in when we try to execute a left/right slide. Following is a list of how our robot acts in regards to joystick input:

Forward: All wheels forward
***Desired motion
Backward: All wheels backwards
***Desired motion
Left: No activity
***Would like to slide left
Right: No activity
***Would like to slide right
CCW turn: Robot turns CW
***Opposite of desired motion
CW turn: Robot turns CCW
***Opposite of desired motion

If anyone has any ideas on how we could fix this problem to allow our robot to slide, we would GREATLY appriciate it. In addition, if anyone has an idea of how to fix our inversion of our CW and CCW turns, that would be wonderful as well!!

[Ether]

Originally Posted by mattom1992

Left: No activity
***Would like to slide left
Right: No activity
***Would like to slide right

What does "No activity" mean? What is the LED on each Jag doing? What are the PWM indicators in the Driver Station showing?

CCW turn: Robot turns CW
***Opposite of desired motion
CW turn: Robot turns CCW
***Opposite of desired motion

Just change the sign of the associated output from your joystick.



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[mattom1992]

Originally Posted by Ether

What does "No activity" mean? What is the LED on each Jag doing? What are the PWM indicators in the Driver Station showing?

When we move the joystick to the left or the right, none of the motors react to the command, hence the "no activity." All of the Jag's LEDs stay yellow and there is no movement in the wheels, and the PWM indicators don't show any changes either.

[Ether]

Originally Posted by mattom1992

When we move the joystick to the left or the right, none of the motors react to the command, hence the "no activity." All of the Jag's LEDs stay yellow and there is no movement in the wheels, and the PWM indicators don't show any changes either.

The default dashboard displays the joystick x-axis. Does it show any response to your left/right joystick motions? Remember that the dashboard updates only once per second.


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[mattom1992]

Originally Posted by Ether

The default dashboard displays the joystick x-axis. Does it show any response to your left/right joystick motions? Remember that the dashboard updates only once per second.

There isn't any response at all given in the display when the joystick is moved left/right.

[shutchman]

what kind of code do you have for your joystick control. we were able to get some wheel movement using the std attack3, but unable to get movement with our code using extreme 3D pro. We will still be working on code, even after the bot ships today. ...Building a test bed w/ the RIO to get the joystick interface worked out with the Mecanum wheels.

[mattom1992]

Originally Posted by shutchman

what kind of code do you have for your joystick control.

Here's a screenshot of our current code for joystick control using the Extreme 3D Pro joystick.

[Alan Anderson]

Originally Posted by mattom1992

Here's a screenshot of our current code for joystick control using the Extreme 3D Pro joystick.

No wonder you aren't getting any noticeable directional control. The "Mecanum - Polar" vi wants a direction specified in degrees. You're giving it the X axis of your joystick, which only ranges from -1 to 1.

I think all you need to do is change it to "Mecanum - Cartesian" and it should work as you expect. (You might also have to negate the sign of your rotation input, depending on whether your joystick twist has positive values to the left or to the right.)

[mattom1992]

We just switched the holonomic drive from "Polar" to "Cartesian" and everything is working properly now. Thanks for all of the help!!

[cmcmaho]

We are also having problems getting the mecanum drive to work. We are using the based Labview Holonimic VI. We are using a Logitech Extreme 3D Pro single joystick with X Y and Axis 3 Throttle. In reading this post we did confirm that we have it set to Mecanum - Cartesian.

Only two of the 4 wheels spin. We are using Talons. Does not seem to be an electrical issue and appears to be a code problem.

Please help
Thanks

[vhcook]

Originally Posted by cmcmaho

We are also having problems getting the mecanum drive to work. We are using the based Labview Holonimic VI. We are using a Logitech Extreme 3D Pro single joystick with X Y and Axis 3 Throttle. In reading this post we did confirm that we have it set to Mecanum - Cartesian.

Only two of the 4 wheels spin. We are using Talons. Does not seem to be an electrical issue and appears to be a code problem.

Please help
Thanks

I'm going to start with the easy question: Which two wheels are moving?

Are your PWM cables plugged into the same ports you specified in Begin.VI?

What color are the LEDs on your Talons when you try to drive forward?