Improvement of Cover Area in Ultrasonic Local Positioning System Using Cylindrical PVDF Transducer

Abstract

This work describes the design of a reflector for a PVDF-based ultrasonic transducer (Piezofilm transducer) to carry out a ultrasonic beacon system, where the covered area be improved and a 3D indoor positioning be guaranteed. The proposed Local Positioning System (LPS) for Mobile Robots (MR) uses simultaneous emissions from ultrasonic beacons. In order to solve the problem of simultaneous emissions from ultrasonic beacons, the well-known technique Direct Sequence Code Multiple Division Access (DS-CDMA) is used. This technique encodes the ultrasonic signal with a 127-bit Gold code for every beacon. It implies the emitted signal by every beacon to have a wide bandwidth. PVDF-based transducers suitably guarantee this requirement. Their cylindrical or semi-cylindrical shape makes the emission pattern not suitable when using them as ultrasonic beacons, often located in the ceiling of an indoor room. To adapt the emission pattern and to increase the covered area in the ground, the design process of a conical reflector is described.