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Investigation of low-sidelobe beampattern controlling methods for acoustic transmitting array of underwater vehicles

He Z., Shi Q., Wu S.

Polish Maritime Research

2017

S 2

103--110

In underwater unmanned vehicles, complex acoustic transducer arrays are always used to transmitting sound waves to detect and position underwater targets. Two methods of obtaining low-sidelobe transmitting beampatterns for acoustic transmitting arrays of underwater vehicles are investigated. The first method is the boundary element model optimization method which used the boundary element theory together with the optimization method to calculate the driving voltage weighting vector of the array. The second method is the measured receiving array manifold vector optimization method which used the measured receiving array manifold vectors and optimization method to calculate the weighting vector. Both methods can take into account the baffle effect and mutual interactions among elements of complex acoustic arrays. Computer simulation together with experiments are carried out for typical complex arrays. The results agree well and show that the two methods are both able to obtain a lower sidelobe transmitting beampattern than the conventional beamforming method, and the source level for each transmitting beam is maximized in constraint of the maximum driving voltage of array elements being constant. The effect of the second method performs even better than that of the first method, which is more suitable for practical application. The methods are very useful for the improvement of detecting and positioning capability of underwater unmanned vehicles.

A geometry and optical property inspection system for automotive glass based on fringe patterns

Xu J., Xi N., Zhang C., Shi Q., Gregory J.

Optica Applicata

2010

Vol. 40, nr 4

827--841

In this paper, an automotive glass inspection system based on fringe patterns is proposed. This system can inspect the 3D shape, reflection normal and transmission distortion of the automotive glass simultaneously. A stereo vision and an iterative algorithm based on the reflection law of the specular surface are utilized to obtain the 3D shape and reflection normal of the inspected part. Then, the bottom reflection of the glass is analyzed such that the line-shifting fringe pattern, based on step wave, is adopted. Additionally, the transmission distortion is defined as an angle between the incoming ray and the outgoing ray for the inspected automotive glass. The method proposed is simpler and more flexible than traditional methods. Finally, the system accuracy has been examined, with the results demonstrating its high accurate performance.