Optimization Design for Connection Relation of Tractor-Trailer Mobile Robot with Variable Structure

Path planned for tractor-trailer mobile robot (TTMR) does not seem to be easily adapted to the case when the number of the trailers increases, thus the repetitive path planning has to be introduced. For this problem, this paper investigates the connection relation of TTMR with variable structure, i.e. the number of the trailers is variable, and deals with the optimization design for it to avoid the repetitive path planning when the number of the trailers increases. After analyzing the motion trajectories of TTMR, we establish the quantitative relationship for the motion characteristics between the transient course and the steady state. Based on which, a new design method to optimize the connection relation for variable-structure TTMR is proposed. In our scheme, the length of each connecting rod between two adjacent bodies is adjusted properly such that the transient deviations of the trailers from the path followed by the tractor will be less than the steady ones. In such a way, the path planned for TTMR can also be appropriate for the case when the number of the trailers varies. The simulations and experiments show the validity of our method

I. Introduction

Tractor-trailer mobile robot is a kind of complicated nonholonomic, underactuated and nonlinear system, which consists of a tractor and multiple trailers. The tractor drives forward and steers the orientation of the system and the trailers move with the tractor passively. As an important transportation system, TTMR can be applied in various situations such as automatic factory, airport, railway station and nuclear environment to deliver materials and convey baggage and goods. Therefore it has a broad prospect of applications in practice.