A Geometric Approach to Motion Control of a Standard Tractor-Trailer Robot

In this paper, we use a simple geometric approach to control the motion of a standard tractor-trailer robot from some initial positions to a goal position. The solution to the motion control problem is proposed in two steps. Firstly, the control laws are proposed that can drive the robot to a goal position whilst observing the mechanical singularities associated with the system. Secondly, the control laws are adjusted so that the robot can avoid any number of fixed obstacles in the workspace and safely reach the goal position. The proposed algorithm is verified using computer simulations.

I. Introduction

A tractor-trailer system consists of a tractor towing an arbitrary number of trailers [1]. A common example in Fiji is the railway locomotive system used for transporting cane to the mill. The trailers are mostly passive so that the overall implementation and operational costs is reduced. The two different trailer systems found in literature are standard and the general trailer systems. The major difference between the two types is based upon the hooking schemes of the trailers. In a standard trailer system, a two-wheeled passive trailer is hitched directly on the midpoint of the rear axle of the tractor robot followed by any additional trailers hitched on the midpoint of the rear axle of the preceding trailer. In contrast, for the general trailer system, each trailer is hitched at a distance away from the midpoint of the rear axle of the preceding trailer / tractor. The reader can refer to [2] for a detailed explanation of the two trailer systems.