Trajectory Generation and Tracking Control for Double-Steering Tractor-Trailer Mobile Robots With On-Axle Hitching

A multisteering tractor-trailer mobile robot (MSTTMR) is a kind of complex multibody system, which consists of a tractor and a chain of steerable trailers. If both the tractor and the trailers can track an identical geometric path, the overall width of the system is only equal to that of the tractor or the trailer. Thus, the robot can perform transport tasks in a narrow space. The MSTTMR with one trailer is referred to as the double-steering tractor-trailer mobile robot (DSTTMR), since the system has two steering inputs. In this paper, trajectory generation and tracking control for the DSTTMR with on-axle hitching are addressed. We first propose an approach to generate the desired full-state trajectory from a desired geometric path given in the Cartesian plane, in order that the desired state trajectories of the tractor and trailer can form the same desired path. Then, a trajectory tracking controller is designed based on the backstepping technique to drive the system's states to converge to their desired trajectories. As a result, the tractor and the trailer can track the desired geometric path simultaneously. Simulation and experimental results are presented to show the effectiveness of the proposed approach.