Motion control of a tractor with multiple trailers

摘要

This paper presents the design and motion control of a practical system where a car-like robotically steerable tractor tows multiple four-wheeled passive trailers. This specific system is rarely dealt with in academic studies but is very commonly applied in real-world industrial applications. The objective is to achieve the trajectory tracking control of the whole system with minimized tracking deviation happening to each trailer. This has long been challenging because of the high degree of non-holonomy caused by the increasing number of linked trailers. This paper simplifies the control problem by considering the whole tractor-trailer system as the iterative linkage of just two types of connection mechanism between axles - the off-hooked connection and the trailer's steering mechanism. In both connection mechanisms, it is designed to make the rear vehicle stably and precisely follows its front vehicle. Since the motion of a passive vehicle is only affected by its preceding vehicle, once the tractor at the very front is controlled to track the reference trajectory, the trajectory tracking control of the whole system can be achieved by iteratively applying the inner tracking property of the two connection mechanisms. The numerical simulation result is also presented to verify the control scheme.