Quote:
Originally Posted by Blue Bomber Man
So I thought about the physics of the rear wheel steering as per Big_dave's warnings and I realized he is almost certainly right. The rear wheel turning causes the rear end of the vehicle to travel in a direction opposite of that the front of the vehicle will be heading.
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There are two effects to consider with rear wheel steering:
1. The direction the car turns is the opposite of the direction the wheel turns (this is like steering a boat with a rudder).
2. The steering is not self centering.
Computer controlled steering could compensate for the second effect. As others have pointed out, with the computer making adjustments, inherently unstable vehicles can be controlled such that, from the operator's perspective, they are stable. Cars are moving in this direction anyway, with computers applying brakes at various wheels during extreme handling situations to maintain vehicle stability.
The first issue cannot be compensated for. Consider what happens to a rear wheel steered vehicle which is parked directly next to a curb. It isn't (in general) possible to pull out forward, because to do so the rear wheel has to turn towards the curb, and the closer rear wheel will run right into the curb as the car moves forward. To pull out from the curb one must back out. Rear wheel steering does mean that in some instances the car just has to be driven differently.
If there is a single rear wheel, and it is both driven and steered, extreme steering angles become feasible. (Losing the drive linkage to another wheel permits this.). Imagine the car parked at the curb with cars very near each bumper. The rear wheel could be turned 90 degrees to move the back end directly away from the curb until it clears the rear car (which due to the narrow rear end, is not nearly so far as for a regular car), and then turned about halfway back towards center to pull the rest of the car out of the parking space.
Hmm, if the rear wheel can turn like that it might be possible to pull forward out of some parking spaces. Method: move as far back parallel to the curb as possible, crank the rear wheel straight towards the curb, drag the butt of the car to it, turn the rear wheel straight (parallel to the curb), move forward keeping the rear wheel parallel to the curb. This will push the front of the car to the left.
I suspect one could get used to driving a car with these properties, but it would be hard to drive this car one day, and a normal car another day.