In indoor navigation of a mobile robot, SONAR has been used for many applications such as self localization, obstacle avoidance, and target classification and localization.
This paper addresses the issue of target classification and localization with a SONAR. In particular, multiple reflections of SONAR sound are used actively and intentionally. As for the SONAR sensor, the multiple reflection has been generally considered as one of the noisy phenomena, which is inevitable in the indoor environments. A method for overcoming the situation is to use only the first reflection for calculating the TOF (Time Of Flight) and ignore the other reflections.
However, these multiple reflections can be a clue for classifying and localizing targets in the indoor environment if those can be controlled and used well. This paper develops a new scanning type SONAR sensor module with a reflection plane which can actively create the multiple reflections. This paper also intends to suggest a new target classification method which uses the multiple reflections.
We approximate the world as being two dimensional and assume that the targets constructing the indoor environment are plane, corner, and edge. Multiple reflection paths of an acoustic beam by a SONAR are analyzed, by simulations and the patterns of the TOFs(Time Of Flight) and angles of multiple reflections from each target are also analyzed. In addition, a new algorithm for target classification and localization is proposed.
The results obtained in the basic experiments and real environmental tests show that the proposed method is proper and has the possibility for various applications.
