Integral Sliding Mode-Based Composite Nonlinear Feedback Control for Path Following of Four-Wheel Independently Actuated Autonomous Vehicles

This paper presents an accurate, fast, and robust path-following control approach for four-wheel independently actuated (FWIA) autonomous vehicles via integrated control of the active front-wheel steering (AFS) and direct yaw-moment control (DYC). The path following is realized through simultaneously converging the yaw rate and lateral velocity to their respective desired values which are generated according to the path-following demand. A novel integral sliding mode (ISM)-based composite nonlinear feedback (CNF) control technique considering the multi-input multi-output and the time-varying tracking reference is proposed, which has combined the advantages of CNF control in improving the transient performance and ISM control in guaranteeing good robustness. Chattering is avoided using a continuous ISM controller instead of generally adopted discontinuous ones based on a multivariable super-twisting algorithm (STA). System uncertainties, tire fore saturations, and variation of the desired-path curvature are compositively considered in the ISM-CNF controller design, with the stability of the overall system proved using Lyapunov method. CarSim-Simulink simulations have verified the effectiveness of the proposed controller in improving the transient path-following performance, inhibiting the overshoots, eliminating the steady-state errors, and rejecting the lumped disturbance considering the tire forces saturations and the varying path curvature.