A backstepping approach for the design of a nonlinear controller for a two-wheeled autonomous vehicle

This paper proposes an innovative approach for the design of a nonlinear controller to stabilize an autonomous mobile robot. The design approach combines a nonlinear control design method with a root-finding algorithm for nonlinear algebraic equations. For the design, the robot model is divided into two parts: a state space model with intermediate control inputs and algebraic nonlinear equations relating the true and the intermediate control inputs. First, a suitable change of variable is applied to the traditional robot dynamics to reveal the strict feedback structure of this state space model. Next, a three-step backstepping control design method is applied to obtain the intermediate control input expressions. Finally, the true control inputs are found by solving iteratively the nonlinear equations that relates intermediate and true control inputs. The proposed design strategy is tested in simulation. The results show that good tracking performances are achieved.