Optimal Steering Control of Long Combination Vehicle with Multiple Steered Units: Minimizing Swept Path Width, Off-Tracking and Rearward Amplification

Abstract

The introduction of Long Combination Vehicles (LCVs) with enhanced load-carrying capacities is a significant advancement in reducing carbon emissions and improving logistical efficiency. By decreasing the number of vehicles on the road, these LCVs contribute to a more sustainable and streamlined freight transport system. However, the increased length and load of these vehicles present challenges in maneuverability in tight spaces and lateral stability at high speeds. This research explores innovative solutions, such as multiple steered and propelled axles, which, when optimally controlled, address these challenges and enhance LCVs performance. The primary focus of this thesis is the lateral dynamics of LCVs, specifically examining lateral off-tracking, swept path width, and rearward amplification. We utilize an A-double long combination vehicle equipped with two steerable and propelled axles as actuators. To improve maneuverability and lateral stability, we develop mathematical expressions for the aforementioned performance characteristics. These expressions serve as cost functions, which are minimized to determine the optimal control inputs for our actuators. The optimization process is conducted using the CasADi toolbox in MATLAB, which provides a robust framework for defining the system dynamics and constraints necessary for the optimization problem. We evaluate the performance of the cost functions across various maneuvers and actuator configurations, highlighting the benefits of multiple actuators with optimal control allocation. The results demonstrate significant improvements in maneuverability at low speeds and lateral stability at high speeds, underscoring the potential of advanced control strategies in enhancing LCVs performance.