Controller Design for Path Tracking of Autonomous Vehicle Incorporating Four-Wheel Steering System

This research aims to model and assess autonomous vehicle controller while including a four-wheel steering and longitudinal speed control. Such a modeling process simulates human driver behavior with consideration of real vehicle dynamics’ characteristics during standard maneuvers. However, a four-wheel steering control improves vehicle stability and maneuverability as well. A three-degree of freedom bicycle model, lateral deviation, yaw angle, and longitudinal speed is constructed to describe vehicle dynamics’ behavior. Moreover, a comprehensive traction model is implemented which includes an engine, automatic transmission, and non-linear magic formula tire model for simulation of vehicle longitudinal dynamics. A combination of proportional integral derivative (PID) longitudinal controller and fuzzy lateral controller are implemented simultaneously to track the desired vehicle path while minimizing lateral deviation and yaw angle errors. Then, A linear quadratic regulator (LQR) based rear steering controller is introduced to represent a performance improvement over front steering only. The longitudinal controller tries to maintain the desired speed through control of the engine throttle while the lateral controller steers the vehicle wheels to follow the pre-defined path. Path tracking simulation is executed through enjoining a referenced safe path to pass a simulated track based on ISO 3888 double lane change maneuver. Both longitudinal and lateral controllers’ simulation results achieved the required performance based on lateral deviation, yaw angle, front steering angle, and vehicle speed. Additionally, the lateral deviation is minimized according to the reference simulated path through the rear steering controller while decreasing vehicle yaw rate and slip angles for front and rear tires.