Here's a time-based VI for you, so you don't have to worry about inconsistant execution rate.
(again, you wire the dbl value (orange wire) through it)
I found that the drivers complained of sluggishness mainly because of the slow ramp-down. Because the ramp-down didn't seem to be neccessary (you can turn out of the way, you can turn sideways, etc), I made it optional to disclude it.
It's a polymorphic VI, in this case meaning you can use it for an array of dbl or a scalar dbl.
The 'setpoint' is your input.
It's under "ramp" at
http://kamocat.com/programming.html#control
I'm still working on something that describes robot movement in turn radius, forward speed, and sideways slip.