Near Field Focusing Behaviour of Airborne Ultrasonic Phased Arrays Influenced by Airflows
This paper investigates the potential use of airborne ultrasonic phased arrays for imaging in outdoor environments as a means of overcoming the limitations experienced by kinect sensors, which may fail to work in the outdoor environments due to the oversaturation of the infrared photo diodes. Ultrasonic phased arrays have been well studied for static media, yet there appears to be no comparable examination in the literature of the impact of a flowing medium on the focusing behaviour of near field focused ultrasonic arrays. This paper presents a method for predicting the sound pressure fields produced by a single ultrasound element or an ultrasonic phased array influenced by airflows. The approach can be used to determine the actual focal point location of an array exposed in a known flow field. From the presented simulation results based upon this model, it can be concluded that uniform flows in the direction orthogonal to the acoustic propagation have a noticeable influence on the sound pressure field, which is reflected in the twisting of the steering angle of the array. Uniform flows in the same direction as the acoustic propagation have negligible influence on the array. For an array impacted by a turbulent flow, determining the location of the focused sound field becomes difficult due to the irregularity and continuously changing direction and the speed of the turbulent flow. In some circumstances, ultrasonic phased arrays impacted by turbulent flows may not be capable of producing a focused sound field.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1123987Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1338
 Z. Zhang, S. Kodagoda, D. Ruiz, J. Katupitiya, and G. Dissanayake, “Classification of Bidens in Wheat Farms,” In Mechatronics and Machine Vision in Practice, 15th International Conference on IEEE, pp. 505-510, 2008.
 D. M. Bulanon, T. Kataoka, Y. Ota, and T. Hiroma, “AE—automation and emerging technologies: a segmentation algorithm for the automatic recognition of Fuji apples at harvest,” Biosystems Engineering, vol. 83, no. 4, pp. 123-135, 2002.
 M. Dunn, J. Billingsley, and N. Finch, “Machine vision classification of animals,” In Mechatronics and Machine Vision 2003: Future Trends: Proceedings of the 10th Annual Conference on Mechatronics and Machine Vision in Practice, Perth, Australia, pp. 9-11, 2003.
 D. Gao, T-F Lu, and S. Grainger, “A new method of feature extraction and location derivation in vineyards using point clouds,” Applied Engineering in Agriculture, vol. 30, no. 2, pp. 293-306, 2014.
 A. J. Fenn, D. H. Temme, W. P. Delaney, and W. E. Courtney, “The development of phased-array radar technology,” Lincoln Laboratory Journal, vol. 12, no. 2, pp. 321-340, 2000.
 W. N.Christiansen, & J. A. Högbom, Radiotelescopes. CUP Archive, 1987.
 R. A. Monzingo, and T. W. Miller, Introduction to adaptive arrays, SciTech Publishing, 1980.
 M. D Zoltowski, and A. S. Gecan, “Advanced adaptive null steering concepts for GPS,” In Military Communications Conference, IEEE, vol. 3, pp. 1214-1218, November, 1995.
 S. C. Wooh, and Y. Shi, “Influence of phased array element size on beam steering behaviour,” Ultrasonics, vol. 36, no. 6, pp. 737-749, 1998.
 L. G. Ullate, and J. L. San Emeterio, “A new algorithm to calculate the transient near-field of ultrasonic phased arrays,” Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on, vol. 39, no. 6, pp. 745-753, 1992.
 A. Neild, D. A Hutchins, T. J. Robertson, L. A. J. Davis, and D. R. Billson, “The radiated fields of focussing air-coupled ultrasonic phased arrays,” Ultrasonics, vol. 43, no. 3, pp. 183-195, 2005.
 L. Azar, Y. Shi, and S. C. Wooh, “Beam focusing behavior of linear phased arrays,” NDT & E International, vol. 33, no. 3, pp. 189-198, 2000.
 W. S. H. Munro, and C. Wykes, “Arrays for airborne 100 kHz ultrasound,” Ultrasonics, vol. 32, no. 1, pp. 57-64, 1994.
 M. Moebus, and A. M. Zoubir, “Three-dimensional ultrasound imaging in air using a 2D array on a fixed platform,” In Acoustics, Speech and Signal Processing, IEEE International Conference on, vol. 2, pp. II-961, April, 2007.
 J. M. Noble, and H. J. Auvermann, “The Effects of Large and Small Scale Turbulence on Sound Propagation in the Atmosphere,” Army Research Lab White Sands Missile Range NM, no. ARL-TR-565, 1995.
 L. Jakevičius, and A. Demčenko, “Ultrasound attenuation dependence on air temperature in closed chambers,” Ultragarsas (Ultrasound), vol. 63, no. 1, pp. 18-22, 2008.
 T. Yang, K. Nadimpalli, and B. Cechet, “Local wind assessment in Australia: Computation methodology for wind multipliers,” Geoscience Australia, viewed 15 September 2015, Retrieved from http://www.ga.gov.au/corporate_data/75299/Rec2014_033.pdf.
 P. Sagaut, and C. Cambon, Homogeneous turbulence dynamics, Cambridge University Press, 2008.