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This paper presents an integrated design method for active trailer steering (ATS) systems of articulated heavy vehicles (AHVs). Of all contradictory design goals of AHVs, two of them, i.e. path-following at low speeds and lateral stability at high speeds, may be the most fundamental and important, which have been bothering vehicle designers and researchers. To tackle this problem, a new design synthesis approach is proposed: with design optimization techniques, the active design variables of ATS systems and passive design variables of trailers can be optimized simultaneously; the ATS controller derived from this approach has two operational modes, one for improving lateral stability at high speeds and the other for enhancing path-following at low speeds. To demonstrate the effectiveness of the proposed approach, it is applied to the design of an ATS system for an AHV with a tractor and a full trailer.

This paper presents a preliminary investigation of the closed-loop driver/articulated vehicle directional dynamics using numerical simulation. To date, a lot of attention has been focused on investigating the closed-loop directional dynamics of driver/single-unit vehicle systems. Little effort has been paid to examining the closed-loop directional dynamics of driver/articulated vehicle systems. Compared with single-unit passenger cars, multi-unit articulated vehicles have unique directional dynamic characteristics. Generally, a driver's behavior for an articulated vehicle is different from that for a passenger car. To investigate the impact of driver behavior on articulated vehicle directional dynamics, three driver models based on dynamic responses of tractor, trailer and combined tractor/trailer, respectively, have been developed.

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.

Vehicle simulators are often used for vehicle system development and driver behaviour study. The target of this study is to design and evaluate an Active Trailer Steering (ATS) system for a Long Combination Vehicle (LCV) with mutiple trailers using a real-time vehicle simulator. A linear yaw-plane LCV model is generated to derive an optimal ATS controller. Then, the controller is reconstructed in LabVIEW and integrated with a vehicle model for a B-train double from TruckSim. The Driver-Software-in-the-Loop (DSIL) real-time simulations are conducted with the vehicle simulator. The DSIL real-time simulations indicate that the ATS controller can effectively improve the LCV's low-speed maneuverability and high-speed stability under the test maneuvers of a low-speed 90-degree turn and a high-speed single-lane change, respectively.

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.