Path Planning for Nonholonomic Multiple Mobile Robot System with Applications to Robotic Autonomous Luggage Trolley Collection at Airports

In this paper, we propose a novel path planning algorithm for the nonholonomic multiple mobile robot system with applications to a robotic autonomous luggage trolley collection system at airports. We consider this path planning algorithm as a Multiple Traveling Salesman Problem (MTSP). Our path planning algorithm consists of three parts. First, we use the Minimum Spanning Tree (MSP) algorithm to divide the MTSP into a number of independent TSPs, which achieves the task assignment for each mobile robot. Secondly, we implement a closed-loop forward control policy based on the kinematic model of the mobile robot to get a feasible and smooth path. The control cost of the path is used as the new metric in solving the TSPs. Finally, in order to adapt to our case, we modify the TSP as an Open Dynamic Traveling Salesman Problem with Fixed Start (ODTSP-FS) and implement an ant colony algorithm to achieve the path planning for each mobile robot. We evaluate our algorithm with simulation experiments and the experimental results demonstrate that our algorithm can quickly generate feasible and smooth paths for each robot while satisfying the nonholonomic constraints.

I. Introduction

The motivation of this paper stems from the need to develop a robotic autonomous luggage trolley collection system at airports. At airports, passengers often use luggage trolleys to carry their luggage to departure gates when they leave and also to a transportation hub when they arrive. For example, the Hong Kong International Airport serves more than 72.9 million passengers every year and around 13,000 luggage trolleys are distributed to deal with the massive passenger flow. A critical concern created by such free access to the luggage trolleys is that passengers usually leave the luggage trolleys where they no longer need them. This makes the luggage trolleys scattered throughout the airport. The airport has to maintain a lot of manpower to collect and return the luggage trolleys to the designated locations so that they can be easily and timely used again and again by other passengers. Because this work is tedious and dull, and the human labor cost is getting higher and higher, there exists a strong demand to use robots to autonomously collect the luggage trolleys and return them to designated pick-up locations without human interventions.