Design and Optimization of a Robust Active Trailer Steering System for Car-Trailer Combinations

This paper presents a robust active trailer steering (ATS) controller for car-trailer combinations. ATS systems have been proposed and explored for improving the lateral stability and enhancing the path-following performance of car-trailer combinations. Most of the ATS controllers were designed using the linear quadratic regulator (LQR) technique. In the design of the LQR-based ATS controllers, it was assumed that all vehicle and operating parameters were constant. In reality, vehicle and operating parameters may vary, which may have an impact on the stability of the combination. For example, varied vehicle forward speed and trailer payload may impose negative impacts on the directional performance of the car-trailer combination. Thus, the robustness of the conventional LQR-based ATS controllers is questionable. To address this problem, we propose a gain-scheduling LQR-based ATS controller. In the design of the proposed ATS controller, at each operating point, the ATS controller is designed using the LQR technique. At an operating point between two established adjacent operating points, the control gain matrix of the controller is determined using an interpolation method. To further improve the directional performance of the car-trailer combination, the weighting matrices of the LQR controller are determined using an optimization algorithm, namely, Generalized Differential Evolution (GDE). The effectiveness of the proposed ATS controller is demonstrated using numerical simulation based on a car-trailer model.