Backstepping Tracking Control Design for a Tractor Robot Pulling Multiple Trailers

Control of tractor-trailer systems is challenging due to their nonlinear, underactuated and highly-coupled properties which gets more crucial with increasing the number of trailers in the system. This paper addresses the tracking control problem of a tractor mobile robot pulling $N$ passive trailers using backstepping control approach. The proposed approach integrates a kinematic controller, that determines the velocity control inputs to track a desired trajectory, with a dynamic controller, that deploys the system dynamics to compute the required torques for the tractor's wheels to achieve the determined velocity control input. While the proposed approach incorporates the system dynamics as well as nonholonomic constraints into the control design, it is shown to be scalable with the number of trailers. The stability of the proposed controller is guaranteed and the simulation results are provided to verify the performance of the proposed controller.