A Practical Fuzzy Logic Controller for the Path Tracking of Wheeled Mobile Robots

This article tackles the path-tracking problem of wheeled mobile robots (WMRs) that are used in the Micro Robot Soccer Tournament (MiroSot). The basic configuration of MiroSot (Figure 1) comprises a football stadium (ground plane) with two teams [1]-[2]. Each team has three WMRs (Figure 2), a camera for image capture, a host computer, and an RF data transmitter. The camera captures the football stadium’s images that are sent to and processed by the host computer. Based on the real-time locations of the robots and the ball and the soccer game strategy, the host computer determines the actions of its team of robots. The objective is to score points by pushing the ball to the opponent’s goal as many times as possible and to prevent the opponent team from scoring points. To achieve this objective, a path has to be generated by the game strategy for the home robot to follow—a path-tracking problem. For each robot, the host computer generates the corresponding control signals driving the wheel at each side to ensure good path-tracking capability. The robot will have both linear and angular displacements until it arrives at the target position. To tackle the path-tracking problem, some other problems have to be solved. First, owing to the nonlinear dynamic and nonholonomic characteristics of the WMRs, the controller design will be a difficult problem, as we do not have a systematic and simple controller design methodology for nonlinear systems. Traditionally, we may derive a mathematical system model from which a suitable controller is designed [3]. However, the model of the WMRs used in MiroSot is very complicated. The WMR dynamic equations are obtained by the well-known Lagrange equations [6]