Trajectory Following Control for Automated Drifting of 4WID Vehicles

It is very significant for autonomous vehicles to have the ability to operate beyond the stable handling limits, which plays a vital role in vehicles’ active safety and enhances riding and driving pleasure. For traditional vehicles, it is rather difficult to control the longitudinal speed, sideslip angle and yaw rate simultaneously when drifting along a given trajectory because they are under-actuated. Nevertheless, for a 4-wheel-independent-drive (4WID) vehicle, it is possible and controllable thanks to its over-actuated characteristics. This article designs a trajectory following control strategy for automated drifting of 4WID vehicles. First, a double-track 7 degree of freedom (7DOF) vehicle dynamic model is established, which incorporates longitudinal and lateral load transfer and considers nonlinear tire models. The controller which proposes a hierarchical architecture is then designed. The upper level vehicle motion controller adopts the sliding mode control to obtain the global resultant total forces and moments to drift along the reference trajectory. The middle level tire force distribution controller then distributes the calculated resultant forces and moments to each wheel considering tire’s frictional adhesion. The lower level actuator controller calculates the steering angle and wheel torque to obtain tire forces. Finally, the effectiveness and feasibility of the hierarchical controller are validated by the co-simulation of Carsim and Matlab/Simulink. Simulation results indicate that the 4WID vehicles can well follow the designed Tai Chi trajectory with variable curvatures, vehicle speeds and sideslip angles, which verifies the correctness and applicability of the designed controller.