Frequency division cooperation based folding steering control for distributed-drive articulated steering vehicles

The traditional articulated steering vehicles rely on the hydraulic steering system and segmented body structure to achieve vehicle steering. The folding steering process exhibits strong hysteresis, which reduces the steering maneuverability and also impacts the autonomous driving performance. This paper proposes a novel control method of folding steering based on differential-hydraulic frequency division cooperation for the redundant drive characteristic of distributed-drive articulated steering vehicles. The main contributions of this paper are as follows: 1) By introducing the speed term into the folding angle control, a position-velocity double closed-loop structure is employed to determine the steering demand torque and achieve the variable steering ratio and accurate control of the folding angle. 2) According to the frequency-domain characteristics of the hydraulic and differential steering systems, a first-order low-pass filtering algorithm is utilized to decompose the steering demand torque into high-frequency and low-frequency components. The high-frequency torque is borne by the differential system, while the low-frequency torque is borne by the hydraulic system, thereby addressing the challenge of cooperative control of multiple actuators. 3) An experimental platform for the distributed-drive articulated steering vehicle is constructed, and the credibility of the dynamic model is experimentally validated. 4) The manipulation and path-tracking performances of the proposed folding steering control method are analyzed. The results indicate that, compared to the hydraulic steering system, the average folding angle rise time and phase delay are reduced by 19.8% and 44.4%, respectively, significantly improving the follow-up performance of folding steering. Furthermore, the average lateral position error and heading angle error in path tracking control are reduced by 38.1% and 27.5%, respectively, which contribute to the electrification and intelligent development of articulated steering vehicles.