Rover Project Post II. How Do Vehicles Steer?

When we made the "tanky" rover turn by turning its two sides in opposite directions, it goes like some awkward jerky thing. So how exactly does those wheeled bots turn?

Tracked vehicles
The track goes forward or backward, it is perfect for moving powerfully forward and backward, but the frictions from sideways when turning is a problem. Tanks can even turn on the spot with experienced drivers moving the treads in opposite direction, sometimes one track at a time during the turn.

To reduce the friction, there are several design methods I gather from the internet.
1. Make the tank as square as possible. Long body causes skid
2. Concentrate the weight in the center, relieve pressure at the treads

4 Wheel Steering 
Using the traditional active steering car as a model to build the steering system is certain one of the choices. All you need is one servo motor for the two active front wheels. The back wheels can either do passive steering or . The disadvantage would be

Rack and pinion www.technologystudent.com/ images3/rkpn2.gif

Most of the 3 wheeled vehicles have a single driving wheel, and they are simple to make. But this leads to problems such as unbalancing and the driving wheel can easily spin. That's why Boe Bot has such a small third wheel in the middle and two driving wheels. 

For vehicles to turn on the spot, you probably can't have more than two driving wheels. The zero-turn lawn movers here is an example. It is basically a two wheeled rover with front two wheels freely moving as balancing/support components.