A control scheme for low speed automated vehicles with double steering

Kinematic relationships for path following are derived for a vehicle with fore and aft steering. In such a vehicle there are two inputs, the front and rear steering angles, which govern the path in the plane motion of the vehicle. In order to follow a desired path a feedback control scheme to set the steering angles in terms of the orientation error and offset from the path is essential. For front wheel steered vehicles the problem has received considerable attention, and many control laws have been proposed; however, how to choose the setting of the rear steering angle is not resolved yet. The very first question is whether to steer the rear wheel in the same direction as the front wheel or in the opposite direction. This paper studies the matter and a number of control schemes are considered and compared. The analysis applies to mobile robots and the class of vehicles with low speed, for which the effect of dynamics of the vehicle becomes negligible. Computer simulation is used to compare the behaviour of a vehicle under the control of each of the schemes for tracking a straight line and a curve