S. Hamed Tabatabaei Oreh

In order to improve the handling and stability of a tractor–semitrailer, a new sliding-mode controller is designed on the basis of a non-linear three-degree-of-freedom model of the vehicle. Three state variables, namely the tractor’s yaw rate, the tractor’s lateral velocity and the articulation angle, are controlled as the target responses using active steering. A new version of the desired articulation angle is proposed so that the rear end of the semitrailer unit is forced to follow the path of the fifth wheel if the proposed reference value is tracked. A 12-degree-of-freedom non-linear model of the articulated heavy vehicle validated by real test data is used to evaluate the control system. The comparative simulation results prove the significant effects of the proposed non-linear control method with respect to a previously designed linear controller on improving the handling and stability performance, especially under severe driving conditions.

In articulated vehicles, one of the main driver’s intentions is that the trailer unit closely follows the path of the tractor unit. However, this expectation is not satisfied even at low speeds. Therefore, it is necessary to develop an appropriate method to reduce or even to eliminate the path tracking error. This article proposes a new desired articulation angle for directional control of the articulated vehicles. The proposed reference value tracking ensures that the rear end of the trailer unit closely follows the trajectory of the fifth wheel. Achieving this goal, a tracking error based on the kinematics of the planar motion of the articulated vehicle is defined. Eliminating the tracking error provides a proper determination of the desired articulation angle between the tractor and trailer unit. A controller designed based on the fuzzy logic theory tracks the proposed reference articulation angle by steering the trailer wheels. To evaluate the effectiveness of the proposed method on both low-speed and high-speed maneuvers, simulations of two maneuvers including low-speed 90° turn and high-speed lane change maneuvers are carried out. The simulation results prove the significant effects of the proposed method on enhancing path following performance.