Appearance-based topological Bayesian inference for loop-closing detection in a cross-country environment

In this paper, an appearance-based environment modeling technique is presented. Based on this approach, the probabilistic Bayesian inference can work together with a symbolic topological map to relocalize a mobile robot. One prominent advantage offered by this algorithm is that it can be applied to a cross-country environment where no features or landmarks are available. Further more, the loop-closing can be detected independently of estimated map and vehicle location. High dimensional laser measurements are projected into a low dimensional space (mapspace) which describes the appearance of the environment. Since laser scans from the same region share a similar appearance, after the projection, they are expected to form a distinct cluster in the low dimensional space. This small cluster essentially encodes appearance information of the specific region in the environment, and it can be approximated by a Gaussian distribution. This Gaussian model can serve as the "joint" between the topological map structure and the probabilistic Bayesian inference. By employing such "joints ", the Bayesian inference in the metric level can be conveniently implemented on a topological level. Based on appearance, the proposed inference process is thus completely independent of local metric features. Extensive experiments were conducted using a tracked vehicle traveling in an open jungle environment. Results from live runs verified the feasibility of using the proposed methods to detect loop-closing. The performances are also given and thoroughly analyzed.