The position sensor feedback circuit used in this steering mechanism is the same as that used in the previous 'ible, a simple potentiometer.
This is the steering rig I build for my ATRT (All Terrain Robotic Trike) vehicle. You can see that in action here, if you like. The panning vision system that I covered recently was built later, to be an add-on module for the ATRT, so covering this subsytem now is kind of back-tracking for me.
I think this system could be adapted to other large 3-or-4 wheeled remote control vehicles or robots. Adding a suspension system or all-wheel-drive would probably complicate the system of tie rods needed, but it could still be done.
Step 1: Build steering knuckles
If you have invested in a welder and a cutting torch, then you will probably enjoy this step a lot more than I did. I did my cutting with a metal blade in a jigsaw, and by hand with a hacksaw. I used a power drill for all of the holes, and lots of nuts and bolts in lieu of welding.
I did get a good deal on nuts and bolts: 80 metric M6 machine screws and matching nuts in a convenient organizing case at the local dollar store. I guess it's because they were metric, that the normal retail stores didn't buy them.
Feel free to use or adapt the imperfect hand-drawn pattern that is shown.