CAE-RLSM: Consistent and Efficient Redundant Line Segment Merging for Online Feature Map Building

In order to obtain a compact line segment-based map representation for localization and planning of mobile robots, it is necessary to merge redundant line segments that physically represent the same part of the environment in different scans. In this article, a consistent and efficient redundant line segment merging (CAE-RLSM) approach is proposed for online feature map building. The proposed CAE-RLSM is composed of two newly proposed modules: one-to-many incremental line segment merging (OTM-ILSM) and multiprocessing global map adjustment (MP-GMA). Different from the state-of-the-art offline merging approaches, the proposed CAE-RLSM can achieve real-time mapping performance, which not only reduces the redundancy of incremental merging with high efficiency but also solves the problem of global map adjustment after loop closing to guarantee global consistency. Furthermore, a new correlation-based metric is proposed for the quality evaluation of line segment maps. This evaluation metric does not require manual measurement of the environmental metric information; instead, it makes full use of globally consistent laser scans obtained by simultaneous localization and mapping (SLAM) systems to compare the performance of different line segment-based mapping approaches in an objective and fair manner. Comparative experimental results with respect to a mean shift-based offline redundant line segment merging (MS-RLSM) approach and an offline version of one-to-one incremental line segment merging (O²TO-ILSM) approach on both public data sets and self-recorded data set are presented to show the superior performance of CAE-RLSM in terms of efficiency and map quality in different scenarios.

I. Introduction

Map building is a key module for autonomous mobile robots since both localization and planning usually depend on the map information of the environment [1], [2]. One typical map representation is the grid map [3], [4], in which the value of each cell represents the probability of being occupied by obstacles. However, the required memory of the grid map grows rapidly with the increase in the environmental size. Therefore, the representation of the environment by features, such as line segments, becomes a popular alternative to the grid map [6], [10], [11], [26]. Compared with the grid map, the line segment map is more compact, consuming less memory and scaling better with the environmental size. Furthermore, the line segment map does not split the environment into grids and, thus, it does not suffer from discretization problems [27].