Cascaded optimal robust controller for trajectory following in autonomous vehicles

A cascaded two-level lateral trajectory control method for a vehicle, the cascaded two-level lateral trajectory control method comprising:

• receiving, by a control system of the vehicle and from a plurality of sensors of the vehicle, a plurality of parameters including at least one vehicle operating parameter and at least one environmental parameter of a road lane in which the vehicle is traveling;
• performing, by the control system, trajectory tracking control (TTC) of the vehicle based on the plurality of parameters, including:
• executing an outer linear quadratic regulator (LQR) control loop to determine both feedback and feedforward control terms and, based thereon, calculate a desired steering angle for the vehicle;
• executing an inner sliding mode control (SMC) control loop with a dynamic reaching phase gain to determine a desired steering torque to achieve the desired steering angle calculated by the outer LQR control loop;
• and
• controlling an electric power steering (EPS) system of the vehicle based on the desired steering torque for improved lateral trajectory control of the vehicle during the TTC, wherein the EPS system is configured to control a steering angle of a pair of wheels of the vehicle, the EPS comprising an electric motor and a systems of gears and linkage.