Design, implementation, and experimental validation of a cascaded trajectory tracking controller for nonholonomic car-like wheeled mobile robots with velocity and steering controllers in the loops

This paper presents a cascaded trajectory tracking controller and a control gains selection procedure for nonholonomic car-like wheeled mobile robots with steering and velocities controllers in the tracking control loops. The trajectory tracking controller enables stable tracking control of trajectories for the car-like mobile robots in the presence of the robot's velocity and steering control latencies. Also, the proposed tracking control solution provides a systematic approach to implementing the tracking controller onto the real car-like mobile robots without requiring any dynamical model of the robot's steering and velocities control systems. This feature avoids the need for ad-hoc control parameters tuning when implementing the tracking controller. The trajectory tracking controller was validated in both simulations and experimentations. The tracking controller has been applied on a car-like pickup truck for experimentations in both on-road and off-road environments. The controller was tested up to the speed of 5.4m/sec in off-road environments. The obtained results confirm the effectiveness of the proposed tracking controller.