Hardware-in-the-loop simulation of automatic steering control: Outer-loop and inner-loop control design

This paper presents a 9-degree of freedom (DOF) vehicle model combined with a closed loop driver model for the purpose of developing vehicle lateral control. The driver model was developed to control the steering angle and uses the lookup table path as a reference for the control input. The proposed outer-loop controller structure for the driver model is a combination of proportional gain control with a yaw effect adaptive fuzzy logic control. A stepper motor model, rack and pinion model, and kinematics model of the steering system are also briefly introduced as an inner-loop sub-system for stepper motor actuated steering (SMAS) system. The proposed inner-loop controller is a closed-loop positioning control for the stepper motor. The performance of the outer-loop and inner-loop controllers were evaluated using predefined trajectory for lanekeeping and double lane change (DLC) maneuvers at 80 km/h constant speed. Both of the controller´s software-in-the-loop simulations (SILS) results were validated using an instrumented automatic steering test rig through the hardware-in-the-loop simulation (HILS). The SILS and HILS results show that the proposed driver model is capable of improving the Y-axis trajectory error and maneuvers significantly and the proposed SMAS system is capable of tracking the desired steering angle position and producing the front wheel steer angle for the use of vehicle model.