A Hierarchical Strategy for the Electro-hydraulic Coupling Steering System on Commercial Vehiclescommercial vehicles, electro-hydraulic coupling steering, characteristic curve, hierarchical strategy

In order to improve the steering performance of commercial vehicles, this paper investigates a novel electro-hydraulic coupling steering (EHCS) system based on the electric power steering (EPS) system and the hydraulic power steering (HPS) system. A hierarchical strategy is proposed for the EHCS system, including a mode judgment controller, an assistance controller and an alignment controller. Fuzzy rules are established in the assistance controller to match the electric and hydraulic power assistance curves, so as to achieve a good assistance effect. The proposed EHCS system and its control strategy are validated in the co-simulation of the Simulink and the Trucksim, the results of which indicate a great improvement in the steering portability and self-alignment, compared with the EPS and the HPS.