Constrained Line-of-Sight Tracking Control of A Tractor-Trailer Mobile Robot System with Multiple Constraints

A tractor-trailer mobile robot system consists of an actuated tractor robot attached with an unactuated trailer robot. The system has a wide range of applications in areas including agriculture, logistics, transportation, etc. Due to the nonlinear and underactuated nature of the system, the tracking control problem is particularly challenging. In particular, while the tractor mobile robot is often well equipped with sophisticated collision avoidance and path following algorithms, the trailer cannot be controlled directly, which can easily deviate from the desired trajectory and result in collisions. In this paper, we propose a novel constrained tracking control algorithm for the trailer to track a desired trajectory, while satisfying multiple performance and feasibility constraint requirements during the operation. To deal with the constraint issue during the tracking control task, both a universal barrier function approach and a novel state transformation scheme are incorporated to deal with constraints of different nature. We show that exponential convergence can be guaranteed, with the convergence rate depending on the control input gain. In the end, a simulation example further demonstrates the efficacy of the proposed algorithm.