Comparison of Path Tracking Control of a Car-Like Mobile Robot With and Without Motor Dynamics

The path tracking model of a car-like mobile robot (CLMR), including its kinematic and dynamic characteristics and the dc motor dynamics, is derived. Due to the hierarchical architecture of the model, the virtual reference input (VRI) (i.e., the reference motor current) is first designed by the first sliding surface, which is set as the linear dynamic pose error of the CLMR. After that, the linear dynamic tracking error of the VRI constructs the second sliding surface for the design of the hierarchical variable structure tracking control (HVSTC). Thus, the direct output (i.e., the motor current) either asymptotically or boundedly tracks the VRI. In this situation, the asymptotic or bounded tracking of the indirect outputs (i.e., the pose of CLMR) is achieved. In addition, the variable structure tracking control (VSTC) based on the above model without the motor dynamics is compared with the model with motor dynamics by HVSTC. To demonstrate the advantageous feature of this paper, the obstacle avoidance (OA) and the target approach (TA) are accomplished by the concept of waypoints. Finally, the simulations for tracking the straight-line and circular paths with the simultaneous OA and TA of the CLMR with and without motor dynamics are compared by the HVSTC and the VSTC, respectively.