Derivation of nonlinear dynamic equations of tractor-trailer mobile robots and their motion control employing input-output linearization control method

In recent years, development and research on wheeled mobile tractor-trailer robots have been extensively increased. Development of such robot is due to increasing maximum load capacity and reducing fabrication and maintenance costs. In this paper, nonlinear dynamic modeling of the tractor-trailer and its motion control are performed. To do this, governing equations of the mobile tractor-trailer robot are firstly derived taken into account nonholonomic constraints of wheels. Assuming lateral and longitudinal non-slippage of the robot wheels, nonholonomic kinematic constraints of the mobile robot are obtained. For dynamic modeling, the Lagrange principle is implemented and the final form of the nonlinear equations of the tractor-trailer robot is derived. Also, the nonlinear dynamics of the system is presented in state-space form and the input-output linearization control method is employed to control point-to-point motion and trajectory tracking. Various simulations are done and the results demonstrate the correctness of the derived nonlinear dynamics and the applicability of the proposed method to control the wheeled mobile robot. Simulations show the nonholonomic constraints of wheels of the tractor and the trailer has a prominent effect on the point-to-point motion of the mobile robot. Moreover, the obtained results indicate the capability of the proposed modeling procedure for the future researches in this field.