Adaptive sliding mode control of a wheeled mobile robot towing a trailer

Abstract

Tractor–trailer systems have been widely used to increase load transportation capacity. Control of these systems started from motion aid facilities in human-driven vehicles to fully autonomous mobile robots in recent years. In fact, tractor–trailer wheeled robot has been proposed as a modular robotic system in which an actuated mobile robot tows a passive trailer. This is a highly nonlinear underactuated system subjected to nonholonomic kinematic constraints, stable tracking control of which is investigated in this article. To this end, first dynamic model and nonholonomic constraints of the system will be developed in the presence of uncertainties and external disturbances. Next, feasible reference trajectories for the system are generated considering the system constraints, and a Lyapunov kinematic control law is used to stabilize tracking errors. Then, an adaptive dynamic sliding mode controller is presented to control the wheeled mobile robot in the presence of external disturbances and uncertainties. Appropriate adaptive rules based on vigorous Lyapunov stability theorems are designed to compensate the wheeled mobile robot upper-bounded lumped uncertainties and automatically update controller gains. Next, the experimental setup is described, and the obtained results are presented and discussed. Experimental and comparative results reveal merits of the proposed approach in successful control of the overall system, that is, a wheeled mobile robot towing a passive trailer, leading to asymptotic tracking of reference trajectories.