Slip-Based Nonlinear Recursive Backstepping Path Following Controller for Autonomous Ground Vehicles

Path following accuracy and error convergence with graceful motion in vehicle steering control is challenging due to the competing nature of these requirements, especially across a range of operating speeds. This work is founded upon slip-based kinematic and dynamic models, which allow derivation of controllers considering error due to sideslip and the mapping between steering commands and graceful lateral motion. A novel recursive backstepping steering controller is proposed that better couples yaw-rate based path following commands to steering angle and rate. Observer based sideslip estimates are combined with heading error in the kinematic controller to provide feedforward slip compensation. Path following error is compensated by a Variable Structure Controller (VSC) to balance graceful motion, path following error, and robustness. Yaw rate commands are used by a backstepping dynamic controller to generate robust steering commands. A High Gain Observer (HGO) estimates sideslip and yaw rate for output feedback control. Stability analysis is provided and peaking is addressed. Field experimental results evaluate the work and provide comparisons to MPC.