Robust Adaptive Controller for a Tractor–Trailer Mobile Robot

A tractor-trailer wheeled robot (TTWR) is a kind of modular robotic system that consists of a tractor template attached with a single or multiple trailers, and hence it is a nonlinear and underactuated system subjected to nonholonomic constraints. Tracking control of such a complicated system is a challenging problem, and that is the focus of this paper. To this end, first dynamics model of a TTWR is developed. Next, feasible reference trajectories are generated to define a trajectory tracking problem. Then, a Lyapunov kinematic control law is elaborated to stabilize tracking errors. Subsequently, a feedback linearizing dynamic controller (FLDC) is designed to generate actuator torques. In a wheeled mobile robot (WMR), like most of real engineering applications, it is impossible to obtain an exact dynamics model due to various unknown, or unpredictable and irregular features. Therefore, the robustness of controllers to overcome uncertainties and external disturbances is necessary. So, a robust adaptive feedback linearizing dynamic controller (RAFLDC) is proposed to control the system using estimated upper-bounds of uncertainties. The stability of the control algorithm is verified using the Lyapunov method. Robustness and effectiveness of the proposed controller, and comparison of results for RAFLDC and FLDC algorithms, is investigated using both simulation studies and experimental implementations, and obtained results will be discussed.