A Probabilistic Framework for Sonar Scan Matching Localization

Scan matching is a popular localization technique based on comparing two sets of range readings gathered at consecutive robot poses. Scan matching algorithms implicitly assume that matching readings correspond to the same object in the environment. This is a reasonable assumption when using accurate sensors such laser range finders and that is why they are extensively used to perform scan matching localization. However, when using other sensors such as ultrasonic range finders or visual sonar, this assumption is no longer valid because of their lower angular resolution and the sparsity of the readings. In this paper we present a Sonar Scan matching framework, the sp1C, which is able to deal with the sparseness and low angular resolution of sonar sensors. To deal with sparseness. a process to group sonar readings gathered along short robot trajectories is presented. Probabilistic Models of Ultrasonic and odometric sensors are defined to cope with the low sonar angular resolution. Consequently, a probabilistic scan matching process is performed. Finally, the correction of the whole robot trajectory involved in the matching process is presented as a constrained optimization problem. (c) Koninklijke Brill NV, Leiden and The Robotics Society of Japan, 2008