Search

Trajectory tracking is one of the main control problems in the context of Wheeled Mobile Robots (WMRs). On the other hand, control of underactuated systems possesses a particular complexity and importance; so it has been the focus of many researchers in recent years. In this paper, these two important control subjects have been discussed for a Tractor-Trailer Wheeled Mobile Robot (TTWMR), which includes a differential drive wheeled mobile robot towing a passive spherical wheeled trailer. The use of spherical wheels instead of standard wheels in trailer makes the robot highly underactuated and nonlinear. Spherical wheels have been used for the trailer to increase robots' maneuverability. In fact, standard wheels create nonholonomic constraints by means of pure rolling and nonslip conditions, and reduce robot maneuverability. In this paper, after introducing the robot, kinematics and kinetics models have been obtained for the system. Then, based on physical intuition a new controller has been developed for the robot, named Lyapaunov-PID control algorithm. Then, singularity avoidance of the proposed algorithm has been analyzed and the stability of the algorithm has been discussed. Simulation results reveal the suitable performance of the proposed algorithm. Finally, experimental implementation results have been presented which verify the simulation results. [ABSTRACT FROM AUTHOR]