Integral Action NMPC for Tight Maneuvers of Articulated Vehicles

We propose an integral action nonlinear model predictive controller (NMPC) for trajectory tracking of an articulated vehicle with an uncertain hitching offset. The controller is intended for complex parking maneuvers including forward and backward movement with tight specifications on the lateral positional tracking error of the trailer. In order to assess performance with uncertain hitching offsets, disturbances, and sensor noise, we conduct extensive hardware-in-the-loop simulations using a dSPACE Scalexio unit. With high-grade sensing, we demonstrate that the closed-loop control system achieves a lateral tracking error of < 3 [cm] in expectation, and an absolute terminal error of < 15 [cm] with high probability p > 0.97. The proposed integral action is shown to be essential in achieving this performance, and the efficacy of the proposed NMPC is evaluated by comparison to alternative MPCs.