SW implementation of Ackermann steering

The desired turn radius at the base_link (middle of the rear axle) is R (R > 0 means left turn, R < 0 means right turn), but the left and the right wheels are circumscribing smaller and larger circles each with the radius R - W/2 and R + W/D.? The corresponding steering angles are: ??L = atan(L/(R-W/2)) and ??R = atan(L/(R+W/2)). This generalizes to the right turn (R < 0).