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This article presents an autonomous steering control scheme for articulated heavy vehicles (AHVs). Despite economic and environmental benefits in freight transportation, lateral stability is always a concern for AHVs in high-speed highway operations due to their multi-unit vehicle structures, and high centers of gravity (CGs). In addition, North American harsh winter weather makes the lateral stability even more challenging. AHVs often experience amplified lateral motions of trailing vehicle units in high-speed evasive maneuvers. AHVs represent a 7.5 times higher risk than passenger cars in highway operation. Human driver errors cause about 94% of traffic collisions. However, little attention has been paid to autonomous steering control of AHVs.

The phase-plane analysis technique has become a powerful tool for analyzing lateral stability of single-unit vehicles. Articulated vehicles, such as car-trailer combinations, consist of multiple vehicle units. Multi-unit vehicles exhibit unique dynamic features compared against single-unit vehicles. For example, a car-trailer may exhibit one of the three unstable motion modes, i.e., jack-knifing, trailer sway and rollover. Considering the distinguished configurations and dynamic features of articulated vehicles, it is questionable whether the phase-plane analysis method based on single-unit vehicles is applicable for analyzing the lateral stability of multi-unit vehicles. In order to address the problem, case studies are conducted to test the effectiveness of the phase-plane method for analyzing the lateral stability of a car-trailer combination, which is represented by a nonlinear vehicle model generated using the CarSim software package.

This paper proposes a model reference adaptive control (MRAC) strategy for active trailer steering (ATS) in order to improve the lateral stability of articulated heavy vehicles (AHVs). Optimal controllers based on the Linear Quadratic Regulator (LQR) technique have been explored to enhance the lateral stability of AHVs; these controllers are designed under the assumption that the vehicle model parameters and operating conditions are given and they remain as constants. However, in reality, the vehicle system parameters and operating conditions may vary. To address the variable payloads of trailer(s), the controller based on MRAC technique is adopted. A three degrees of freedom (DOF) linear yaw-plane tractor-semitrailer model is generated to design the control law. The reference model is also developed using the linear yaw-plane model with the LQR technique. The effectiveness of the MRAC controller is demonstrated using numerical simulations under an emulated single lane-change maneuver.

An optimal preview controller is designed for active trailer steering (ATS) systems to improve high-speed stability of articulated heavy vehicles (AHVs). AHVs' unstable motion modes, including jack-knifing and rollover, are the leading course of highway accidents. To prevent these unstable motion modes, the optimal controller, namely the compound lateral position deviation preview (CLPDP) controller, is proposed to control the steering of the front and rear axle wheels of the trailing unit of a truck/full-trailer combination. The corrective steering angle of the trailer front axle wheels is determined using the preview information of the lateral position deviation of the trajectory of the axle center from that of the truck front axle center. In turn, the steering angle of the trailer rear axle wheels is calculated considering the lateral position deviation of the trajectory of the axle center from that of the trailer front axle.