Drive motor spinning out...need slower response

[grosh]

We geared our robot for speed...maybe to much. We need to slow the response of our joysticks to the drive motors to keep us from spinning out. We are using talons and labview. Any help?

[Alan Anderson]

Here's a simple option that might work well for you: in the wire between the joystick axis and the Robot Drive function, insert a cube function.

Right-click the wire. From the popup menu, choose Insert -> Numeric Palette -> Expression Node (it's a rectangle saying EXPR). You'll get a small orange box with right-pointing arrows on either end. Click the blank space between the arrows and type x*x*x.

Now, small motions of the joystick will give you very small changes in the motor control value. Medium motions of the joystick will give you smallish changes in the motor value. But full travel of the joystick will still give you full power.

[Mark McLeod]

You could modify the response curve of your joystick to emphasize the low end more
Like this:
http://team358.org/files/programming/ControlSystem2009-/LabVIEW/JoystickCurve2.jpg

Or your could cut the top speed by multiplying the joystick axis by a percentage, like .75, before feeding it to the Motor Output.

[Ether]

We geared our robot for speed...maybe to much. We need to slow the response of our joysticks to the drive motors to keep us from spinning out.

"Spinning out" and "need to slow the response" sounds like you geared your drivetrain for too much acceleration.

If that's the case, take a look at the "slew rate limiting" in Eric VanWyk's article here: http://thinktank.wpi.edu/article/140

[grosh]

[QUOTE=Ether;1239130]"Spinning out" and "need to slow the response" sounds like you geared your drivetrain for too much acceleration.

QUOTE]

Ether you're right. We have an acceleration issue. If the driver is careful with the sticks, doesn't apply to much throttle to soon, she can avoid spinning out. With practice she could probably get used to it but I was hoping for a pragramming fix to help her.

We will try these suggestions out today. I'll let you know how it works. Thanks!