The Ackermann steering geometry is a geometric arrangement of the couplings in the direction of a car or other vehicle designed to solve the problem of the wheels inside and outside of a turn needing to draw circles of different spokes. It was invented by the German car builder Georg Lankensperger in Munich in 1817, then patented by his agent in England, Rudolph Ackermann (1764-1834) in 1818 for horse-drawn carriages. Erasmus Darwin may have a prior claim as the inventor dating back to 1758.
The intention of the Ackermann geometry is to avoid the need for the tires to slide sideways as you follow the path around a curve. The geometric solution to this is that all wheels have their axes arranged as circle radii with a common center point. As the rear wheels are fixed, this center point must be in a line extended from the rear axle. The intersection of the front wheel axles in this line also requires the inner front wheel to rotate, when steering, through an angle greater than the outer wheel.
Instead of the previous "rotating" direction, where both front wheels revolved around a common pivot, each wheel gained its own pivot, near its own hub. Although more complex, this arrangement improves controllability by preventing large entries of variations in road surface from being applied to the end of a long lever arm, as well as considerably reducing the longitudinal displacement of the steering wheels. A union between these hubs pivots the two wheels together, and by the careful arrangement of the dimensions of the connection the Ackermann geometry could be approximated. This was achieved by making the articulation not a simple parallelogram, but by making the length of the track bar (the movable link between the hubs) shorter than that of the axle, so that the steering arms of the hubs "When the steering was moved, the wheels rotated according to Ackermann, with the inner wheel turning further. If the track bar is placed in front of the axle, instead it should be longer in comparison, thus preserving this same "toe out".