Intelligent Path Following of Articulated Eight-Wheeled Mobile Robot with Nonholonomic Constraints

Path following problem is of considerable importance in articulated wheeled mobile robots due to their complex structure, wheel slippage and the possibility of robot's instability and overturn. In these robots, the path following problem can be divided into two separate problems, including following the desired path by one of the robot's articulated bodies and adjusting the robot articulation angle by another articulated body. In this research, the MFL-CPS algorithm is utilized for following the desired path. In this algorithm, the tracking point is chosen based on curvature-derived point selection algorithm (CPS), then the robot follows the selected point using a Mamdani fuzzy logic controller (MFL). In order to adjust the articulation angle, first, the robot's kinematic equations are derived. The desired articulation angle is defined such that neither instability nor wheel slippage happens while the robot is in motion. Afterwards, in order to put the robot in the desired articulation angle, a PI controller is used. Finally, the proposed path follower for following a piecewise linear path is implemented on an eight-wheeled mobile robot, built from joining two four-wheeled robots with nonholonomic constraints. Obtained results show the favorable performance of the eight-wheeled robot, such that for a 17.31 meters path, the tracking root mean square errors (TRMSE) of the front and rear four-wheeled robots are 0.64 and 0.03 meters, respectively.