On Some Low-Cost Tracking Controllers for Mobile Robots

Abstract

The article addresses the problem of developing low-cost controllers used in tracking control for mobile robots. A simplified dynamic model that can well characterize the wheeled mobile robots with two degrees of freedom is first proposed. The control system structure involved contains two control loops for controlling the forward velocity and the angle between the heading direction and the x-axis. The reference trajectory of the robot is obtained by employing the artificial potential field method used in obstacle avoidance, accompanied by some simple computations in terms of the tracking errors for the x- and y-axes and of the maximum accepted values for these errors. In addition, the authors present development methodologies for three types of tracking controllers: the PI controllers, a version of PI-fuzzy controllers, and a version of sliding mode-PI controllers, based on the Extended Symmetrical Optimum method applied to the basic linear PI controllers and by adding nonlinear features of fuzzy- or sliding mode-type for obtaining control system performance enhancement. Simulation results are provided to validate the proposed dynamic model and navigation controllers.