Path tracking control of a tractor-trailer wheeled robot kinematics with a passive steering angle

In the present work, we propose a trajectory tracking control method for the tractor-trailer wheeled robot in that both the trailer and the tractor are able to precisely track an identical target trajectory curve at a low speed. To this end, two key innovations are presented as follows. Firstly, a passive steering angle and its gear steering mechanism are introduced for steering the trailer, so that it follows very well the trajectory of the tractor. Secondly, the motion laws of the tractor-trailer wheeled robot with a passive steering angle are established by analyzing the non-holonomic constraints. On this basis, a standard method is applied to establish its kinematics and dynamics models. The original motion task of the tractor-trailer wheeled robot is then transformed into a curvature tracking control issue of the tractor via a dynamic tracking target. Finally, the integral sliding mode control and the linear quadratic regulator are combined to design two proper torque controllers for implementing a prescribed motion task. Numerical simulation results show that both the tractor and the trailer can accurately move along the desired path simultaneously by adopting a dynamic tracking target and an appropriate passive steering angle, even though the tracking speed error of the tractor is large.