An energy-efficient adaptive angle tracking strategy of electro-hydraulic hybrid steering system for unmanned commercial vehicles

Aiming at the angle tracking control problem and high energy consumption issues arising from the fixed motor speed control in the hydraulic assist module of the electric-hydraulic hybrid power steering (EHHS) system of commercial vehicles in unmanned driving mode, an energy-efficient angle tracking strategy is proposed. Based on the establishment of a comprehensive dynamic model for the steering system, and taking into account the dynamic characteristics of the EHHS system and uncertain factors such as external disturbances, an angle-tracking and electro-hydraulic coordinated controller (ATEHC) is designed. This coordinated controller employs a fast terminal sliding mode controller with integral elements to calculate the desired hydraulic steering assist torque based on the target steering angle. Furthermore, an adaptive estimation term is designed for real-time compensation to suppress the effects of nonlinearity and external disturbances, reduce chattering, and enhance the robustness of the system. Additionally, an adaptive hydraulic power assist controller (AHPAC) is designed to address the issue of the non-direct correlation between motor control input and valve output. AHPAC employs an ADRC-GAPID cascade control, where the Genetic Algorithm (GA) is utilized to optimize the PID parameters. AHPAC modulates the motor voltage based on the desired hydraulic assist torque, thereby achieving variable motor speed and output hydraulic torque. Simulation results demonstrate that the proposed angle tracking control strategy improves angle tracking accuracy while ensuring smooth assist torque output, achieving adaptive coordination of electric and hydraulic assist torques, effectively reducing system energy consumption. Finally, bench tests confirm that the control strategy meets the steering angle tracking requirements of unmanned driving modes in commercial vehicles and exhibits excellent energy-saving effects.