VASC Seminar Announcement ========================= Speaker: Roman Kuc Affiliation: Yale University E-mail: roman.kuc@yale.edu Date: Monday, August 12 Time: 3:30pm Place: NSH 1507 Appointments: Louise Ditmore (please make arrangements before 1:00 Friday. Dr. Kuc is available 1-3, 5-6 on Monday) Title: RECOGNIZING CORNERS WITH AN OBLIQUELY-ORIENTED CONTINUOUSLY-MOVING MULTI-POINT SONAR Abstract: This talk investigates the information contained in conventional Polaroid sonar echoes from a hallway probed by a moving robot. Right-angle corners normally occur in indoor environments and form strong retro-reflectors that exhibit properties that allow its echoes to be identified. A sonar mounted on a moving robot is oriented to be oblique to the travel direction. As the sonar passes over a corner, it observes a sequence of strong echoes that have a temporal coherence, which we term a glint. Our sonar contains a conventional Polaroid 6500 ranging module controlled in a novel fashion to convert echoes into a multi-point sequence, whose density relates to the echo amplitude. The resulting pseudo-amplitude sonar (PAS) scans reveal corner glints, whose forms are predicted by a forward model. An algorithm identifies corner glints and localizes the corner by performing a two-dimensional search to find corner coordinates that produce readings that match the data in a least squared error sense. Applying glint size and quality-of-match criteria differentiate corner glints from those produced by cylindrical retro-reflectors. Sample PAS scans from specular and heterogeneous sides of a hallway are compared with conventional time-of-flight sonar maps and demonstrate that multi-point sonar reliably recognizes and accurately localizes corners.