Electronic architecture for air coupled ultrasonic pulse-echo range finding with application to security and surface profile imaging

Ultrasonic range finding instruments are utilized, e.g., for measuring liquid levels and distance to parking obstacles. However, instruments designed using the conventional electronic architectures to drive the ultrasonic transmitters cannot provide an operating range beyond a few meters for a flat solid wall with normal incidence when powered by a low voltage battery. This both limits the applicability of the existing instruments and makes it difficult to demonstrate their feasibility for new applications. The architecture described here combines a DC/DC boost converter with semiconductor switches, enabling a scalable increase in the operating range for both pulse-echo and pitch-catch modes of operation. It was fully prototyped and successfully tested for novel applications involving ultrasonic range finders, specifically intrusion detection and surface profile imaging. The limitations of the profile sensing device are rather restrictive as it only operates at the incidence angles below 18°, but this device can be developed further. The developed security system was found to be quite practical in its present state

The high frequency flexural ultrasonic transducer for transmitting and receiving ultrasound in air

Flexural ultrasonic transducers are robust and low cost sensors that are typically used in industry for distance ranging, proximity sensing and flow measurement. The operating frequencies of currently available commercial flexural ultrasonic transducers are usually below 50 kHz. Higher operating frequencies would be particularly beneficial for measurement accuracy and detection sensitivity. In this paper, design principles of High Frequency Flexural Ultrasonic Transducers (HiFFUTs), guided by the classical plate theory and finite element analysis, are reported. The results show that the diameter of the piezoelectric disc element attached to the flexing plate of the HiFFUT has a significant influence on the transducer's resonant frequency, and that an optimal diameter for a HiFFUT transmitter alone is different from that for a pitch-catch ultrasonic system consisting of both a HiFFUT transmitter and a receiver. By adopting an optimal piezoelectric diameter, the HiFFUT pitch-catch system can produce an ultrasonic signal amplitude greater than that of a non-optimised system by an order of magnitude. The performance of a prototype HiFFUT is characterised through electrical impedance analysis, laser Doppler vibrometry, and pressure-field microphone measurement, before the performance of two new HiFFUTs in a pitch-catch configuration is compared with that of commercial transducers. The prototype HiFFUT can operate efficiently at a frequency of 102.1 kHz as either a transmitter or a receiver, with comparable output amplitude, wider bandwidth, and higher directivity than commercially available transducers of similar construction

Sonar ultra-sónico para pequenos robots

Mestrado em Engenharia Electrónica e TelecomunicaçõesO presente documento tem como objectivo descrever a implementação de um Sonar ultra-sónico para pequenos robots. O tema desta dissertação surgiu a partir da observação das limitações existentes nos sistemas ultra -sónicos de detecção de obstáculos disponíveis para os sistemas robóticos. Assim, foi decidido construir um array utilizando sensores de baixo custo. Estes transdutores apresentam contudo um diâmetro com o dobro do com- primento de onda o que hão permite, à primeira vista construir um array que evite aliasing espacial. Para resolver este problema é proposto um array do tipo 1.5D que permite evitar o aliasing. Foi desenvolvido todo o hardware de geração e aquisição de sinal que inclui um DSP de baixo custo para a realização dos algoritmos. Foi igualmente desenvolvido o software de processamento digital de sinal para detecção dos obstáculos a partir dos sinais captados pelo array. Testes realizados com o sistema confirmaram a correcta detecção de obstáculos num feixe de ±40°.This document describes the practical implementation of an ultrasonic Sonar for small robots. This idea comes up from the observation of the limita- tions of existing obstacle avoidance ultrasonic systems available for robotic systems. So it was decided to build an ultrasonic array with low cost sen- sors. These transducers have a diameter that is twice the wavelength of the emitting signal making them on a first sight useless to build an aliasing free array. To solve this problem a 1.5D array is proposed leading to an alias free array. All the generation and acquisition hardware was developed which includes a low cost DSP for real time signal processing. The algorithm for obstacle detection using the signals acquired by the array was also developed. Real field tests showed the ability of the system to detect obstacles in a beam of ±40°

Sensors and Systems for Indoor Positioning

This reprint is a reprint of the articles that appeared in Sensors' (MDPI) Special Issue on “Sensors and Systems for Indoor Positioning". The published original contributions focused on systems and technologies to enable indoor applications