Adaptive and predictive non linear control for sliding vehicle guidance: application to trajectory tracking of farm vehicles relying on a single RTK GPS

When designing an accurate automated guidance vehicle system, a major problem is sliding and pseudo-sliding effects. It is especially the case in agricultural applications, where a five centimeters accuracy with respect to the desired trajectory is required, even if vehicles move on a slippery ground. Previous works have established that RTK GPS was a very suitable sensor to achieve automated guidance with such a high precision: several control laws have been designed for vehicles equipped with that sensor, and provide the expected guidance accuracy as long as vehicles do not slide. Further control developments have been previously proposed to take sliding into account: guidance accuracy in slippery environment has been shown to be preserved, except transiently at beginning/end of curves. In this paper, design of such a control law is first recalled and discussed. Model predictive control method is then applied in order to preserve guidance accuracy even during these transitions. Finally, the global control scheme is implemented, and improvements with respect to previous guidance laws are demonstrated through full-scale experiments.