Luftultraschall-Sender-Empfänger-System für einen künstlichen Fledermauskopf

Abstract

Bats orientate themselves in their natural environment by transmitting ultrasonic pulses and putting together the reflected echoes to a three-dimensional information. In millions of years this sonar system evolved astonishing navigation achievements. This special ability of the bats is under the aspect of bionic development starting point and inspiration for the field of robotic navigation and automated objects recognition with the aid of improvement of the detection of small objects. Up to now the ultrasonic system of bats is not technically transferable, because the presently available ultrasonic transformers do not possess the required properties. Hence, in the present work ultrasonic transmitters and receivers were developed which correspond to a great extend both with regard to the frequency area and transmitted sound pressure together with the sensitivity of the transmitting and receiving system of bats. To fulfil these requirements, a special Polypropylene with the name EMFi (Electro Mechanical film) was used as transducer material, the cellular structure of which results in a very high piezoelectric d33 constant and a very good adaptation to air. This new type of material required extensive numerical and measuring technical research of the material behaviour in order to improve the behaviour of the transformer. Additionally to the above a material data file was compiled on the basis of simulation and measuring results, which describes the piezoelectric and acoustic behaviour of the EMFi material approximately. The small size, the low weight and the very good acoustic properties of the ultrasonic transmitters and receivers developed in the course of this work allowed for the first time the construction of an artificial bat head which corresponded very approximately with the biological one. Therefore biologists will be able to utilise this artificial bat head for further research. Thereby the high frequency range of the ultrasonic transmitters and receivers developed in this work, allows for the first time, the whole frequency spectrum of bats to not only be generated but also to be measured.