[Tom Line]

I can think of a couple ways to do this.

Foot steering could be accomplished by using a turntable (torsion spring return to center) that you put your foot and twist to turn, and having an absolute encoder or potentiometer give the feedback to a control system that controls the electric motor.

The actual steering could be accomplished through an electric rack and pinion setup - you may be able to get one cheap off the net for existing cars.

Or, conversely, you could make your own rack and pinion setup.

Or, you could run a small motor in a transmission to a winch with wires running to the end of each A-arm. This is probably the simplest as you wouldn't have to worry about any type of mechanical alignment with the steering system and a rack.

I'd also look at RC cars. They use a servo with a few simple lever-linkages for steering. You could do the same here, and use an electric motor with feedback through a small transmission as a pseudo-servo.

Finally and probably the most simple would be directly turning the steering column with a motor through a small transmission. You could use a lever and a super-shifter transmission so that even has a neutral gear so that you could hand steer it!

To tell you the truth - this is all something that many of the First Robotics team here could pull off with their machining facilities. Maybe you could even hit up someone for one of the old IFI control systems to program it all for you.

Edit - it looks like Don and I had a lot of the same ideas, but I just thought of another one. Instead of a turntable, use a lever that turns, similar to the way the hand on a clock turns. Put a shoe-catch like they have on long-distance bikes that the toe of your shoe goes in. Then he rocks his ankle left to go left and right to go right. This would be easier than a turntable though it would work on the same philosopy. It would be pretty easy to make.