Nonlinear Disturbance Observer-Based Fuzzy Adaptive Finite-Time Dynamic Surface Formation Control of Tractor–Trailer Wheeled Mobile Robots

Abstract

In this paper, the trajectory tracking control problem for a team of nonholonomic tractor-trailer wheeled mobile robots has been investigated based on the leader-follower strategy in the presence of structural uncertainties and external disturbances. For this purpose, the kinematic and dynamic equations of the formation of tractor-trailer robots are presented and leader-follower's model is produced by defining the state error vector at first. Then, a nonlinear disturbance observer is designed by using the formation dynamic model to estimate and compensate the external disturbance and a new model of the system is obtained. In the following, a finite-time dynamic surface controller has been designed and presented by considering an observer-based model. The proposed scheme ensures closed-loop signals boundedness and fast convergence of tracking errors in a limited time. Furthermore, the parametric uncertainties are estimated by using a fuzzy adaptive estimator with a great accuracy. Finally, the finite time stability of the closed-loop control system is proved by Lyapunov theory and the effectiveness of proposed algorithm is shown by simulations.