Well, i’m trying to get the pivot to follow the line, even though i’m using the steer axle to position. It is proving quite challenging - but that’s the reason for the whole project.
So it end up being an integral of the pivot position error made by the atan of the steer distance over speed plus the error of vehicle heading and ab segment heading, then using the derivative of that to not oversteer when correcting the pivot xte added to the pivot integral which is also the atan of its value over speed.