Cascaded Steering Control Paradigm for the Lateral Automation of Heavy Commercial Vehicles

Abstract

The nonlinearity and complexity of the lateral dynamics of heavy commercial vehicles (HCVs) and their steering subsystems usually pose considerable challenges in realizing automatic lateral control for HCVs. In this article, a novel cascade control paradigm is presented for the automatic lateral guidance control of HCVs, which is equipped with an electrohydraulic coupling power steering (EHCPS) system. The objective is to propose a control framework for the satisfactory trajectory tracking performance of HCVs. This control framework consists of an outer vehicle chassis dynamics controller and an inner steering controller, which are implemented to mitigate the issues associated with the trajectory tracking process due to the intrinsic parameter-varying nonlinearity of the vehicle lateral dynamics model and the steering tracking process caused by the complex mapping relationship between the steering wheel angle input and front wheel angle output, respectively. Using the linear parameter-varying (LPV) technique as a general framework, an outer loop controller is designed to produce the desired front wheel angle, which features a gain scheduling mechanism to cope with the time-varying longitudinal velocity. Based on the analysis of the simplified physical model of the EHCPS system, a feedforward set-point scheduling inner loop controller with sliding-mode observer (SMO) is proposed to ensure good tracking performance of the front wheel angle for the steering subsystem. Through experimentation, conducted on the hardware-in-the-loop (HIL) test platform for HCV automatic lateral control, the feasibility and effectiveness of the proposed cascade steering control paradigm are demonstrated.