Submarine Sonar Wet End Development in ASELSAN Muhammed N. enlik, - - PDF document

UDT 2020 UDT Extended Abstract Template Presentation/Panel

Submarine Sonar Wet End Development in ASELSAN

Muhammed N. Şenlik, Erdem Çağatay, Ömer Özdemir, Osman Yalçınkaya, Kerim Çepni, Aykut Şahin ASELSAN, Ankara, Turkey

Abstract — PREVEZE Class Submarines are integral part of Turkish Navy Submarine Fleet. They are about to enter half life-cycle full modernization phase. In the context of this phase, the whole wet end made of the analog

• utput sensors shall be replaced with the modern digital output sensors. ASELSAN is the prime contractor for the

modernization of wet end. Six different sensors, most of which operate at the low frequency regime, shall be designed, produced and verified. In this paper, the concentration shall be on low frequency transducers, specifically

• n their characterization. The low frequency measurements typically require deep water reservoirs due to increased

wavelength, or equivalently to prevent reflections from surface and bottom of the reservoir. There are several approaches to overwhelm this problem. Bobber has discussed many of the methods in his classical book ―Underwater Electroacoustic Measurements‖, especially concentrating on the near-field methods. Here, we will walk through the most classical approach, ―pulse-echo measurement‖, and use the single cycle measurement technique with the aid of equivalent circuits. We will conclude with the presentation of the measurements taken at ODTU Yalıncak Facility, which is in the close proximity of ASELSAN, Ankara. The facility has a reservoir of 9 m depth.

1 Introduction

Submarines are integral part of the navies due to their capability of invisibility. The price comes with the need

• f sole trust to the sonars, a combination of both wet end

and algorithms. The use of active sonar is not preferred since it removes the invisibility cloak on the submarine. Passive sonars with the lowest achievable frequency are

• preferred. The upper end of the frequency band is

determined by the need and/or sonar dome; whereas the low frequency end is determined by the finite input impedance of the receiver circuitry and the self-noise of the submarine. The typical lowest frequency is in the

• rder of few 10’s of Hz for a flank array [1]-[3], whereas

a few 100’s of Hz for a cylindrical array [1]-[3]. In this work, an element so called ―stave‖ of a cylindrical array (cylindrical hydrophone array), which is an integral part

• f PREVEZE Class Submarines of Turkish Navy

Submarine Fleet, shall be characterized in the low frequency regime, namely below 1 kHz. A general characterization method, pulse-echo measurement, is given in [4]. It is critical that a sufficient depth in the measurement area is present, in order to successfully discriminate the input and reflected pulses. Also, in order to optimize the use of depth, all equipment should have high bandwidth, to prevent transients and increase the possibility of single cycle measurements. When these criteria are not met, the use of near field measurement techniques can be used. These techniques are investigated by Bobber in his classical book ―Underwater Electroacoustic Measurements‖ [5]. Both of these methods, DRL and Trott, require tight alignment of the projector and hydrophone sometimes in the order of mm’s. There are also various methods for characterization of the equipment at low frequency

• regime. However, these methods are mostly useful for the
• mnidirectional hydrophones and projectors. In the case
• f characterization of a directional hydrophone, it may be

required to use travelling wave methods based on pulse- echo measurement. In this work, measurement of the free-field sensitivity (RVS) of a directional hydrophone is presented and compared with the results obtained from equivalent

• circuit. First, the measurement setup is described and the

reference measurements are presented. The measurement data is verified using equivalent circuit approach. Then, the measurement method for a directional hydrophone is

• given. Both the experimental and simulation results are
• presented. It is shown that they are in good agreement

and can be used for calibration and/or verification of

• utput of mass production.

2 Reference Measurement

For reference measurements, a pulse-echo measurement setup shown in Fig. 1 is being constructed at ODTU Yalıncak Facility, in the close proximity of ASELSAN,

• Ankara. At the measurement point, the reservoir has a

depth of 9 m. The reference projector and hydrophone is placed around 4.5 m depth to maximize the maximum allowable pulse width which is close to 5 ms, rather than advised one which is 2/3 of actual depth [5]. The reference projector is Neptune D11 [6] and the reference hydrophone is Neptune D140H [6]. The measurement location suffers from electromagnetic interference. A Butterworth filter with a low frequency cut-off at 100 Hz is used to clean the output of the hydrophone from the environmental noise.

UDT 2020 UDT Extended Abstract Template Presentation/Panel

• Fig. 1. Test setup

To verify the measurements, an equivalent circuit shown in Fig. 2 is constructed using Pathwave Advanced Design System (ADS) of Keysight Technologies [7]. ADS is preferred due to its ability to use frequency dependent model in the transient solutions.

• Fig. 2. Equivalent circuit of reference measurement setup.

The equivalent circuits parameters are calculated using [8], assuming that the reference transducers have a spherical shape. The material is assumed to PZT-4 for D11, whereas PZT-5H for D140H. The main motivation in this work is the characterization

• f a directional hydrophone below 1 kHz. Fig. 3 shows a

comparison of measurement data and output obtained from equivalent circuit. As can be seen, the results are in good agreement. The transient response at 11 kHz due to the finite bandwidth of the projector is well resolved with the equivalent circuit.

• Fig. 3. Measurement data and equivalent circuit output.

Measurement and simulation are performed at 500 Hz.

3 Actual Measurement

The actual hydrophone to be characterized is a directional hydrophone, which is approximately 65 cm in length. A baffle composed of a hard and soft impedance material is implemented inside the hydrophone [8] [9]. This gives the directional characteristics of hydrophone, which loses its characteristics below 1 kHz. The preliminary measurements indicate that the hydrophone has a very narrow bandwidth, which is predicted by [8] [9]. An equivalent circuit based on Error! Reference source not found. including the transfer function of the hydrophone is implemented.

• Fig. 4 shows the measurement data and equivalent circuit
• utput at 500 Hz. The results show that both

measurement data and equivalent circuit data are in good

• agreement. The initial rise at the first cycle of the output

is due finite response of the filter used in the

• measurements. The variations at the higher cycles are due

to the narrow bandwidth of the hydrophone.

• Fig. 4. Measurement data and equivalent circuit output.

Measurement and simulation are performed at 500 Hz.

• Fig. 5 also shows the measured RVS data below 2 kHz.

The dip around 1 kHz corresponds to the resonance of the soft and hard impedance materials.

UDT 2020 UDT Extended Abstract Template Presentation/Panel

• Fig. 5. RVS data below 2 kHz.

4 Conclusion

PREVEZE Class Submarines are integral part of Turkish Navy Submarine Fleet, which are about to enter half life- cycle full modernization phase. In the context of this phase, the whole wet end sensors shall be replaced by ASELSAN as the prime contractor. Cylindrical Hydrophone Array is one of the wet end sensors, which

• perate to the low end of the frequency band. The mass

number of sensors used in the array should be calibrated with a limited depth reservoir. The presented approach, which is a combination of both measurement data and equivalent circuit can be checked the validity of the measurements.

References

[1] A. D. Waite, SONAR for practising engineering, 3rd

• ed. John Wiley & Sons, Ltd., 2002.

[2] https://www.atlas-elektronik.com/ [3] https://www.thalesgroup.com/en [4] P. A. Levin, Calibration of hydrophones, B & K Technical Review, 3 – 17 (1973) [5] R. J. Bobber, Underwater electroacoustic measurements, Peninsula Publishing, Los Altos, 1988. [6] http://www.neptune-sonar.co.uk/ [7] https://www.keysight.com/zz/en/products/software/ pathwave-design-software/pathwave-advanced- design-system.html [8] J. L. Butler, C. H. Sherman, Transducers and arrays for underwater sound, 2nd ed. Springer, 2016 [9] S. H. Ko, H. H. Schloemer, Signal pressure received by a hydrophone placed on a plate backed by a compliant baffle, J. Acoust. Soc. Am. 89 (1991)

Muhammed N. Şenlik

• M. N. Senlik has received his B.S., M.S. and Ph.D. from

Bilkent University in 2002, 2005 and 2015, respectively, all in Electrical and Electronics Engineering. He is with Acoustic Systems System Engineering Department of ASELSAN since 2011.

Erdem Çağatay

• E. Çağatay has received his B.S. and M.S. from Bilkent

University and TOBB ETÜ University in 2014 and 2018, respectively, both in Mechanical Engineering. He is with Acoustic Systems System Engineering Department of ASELSAN since 2019.

Ömer Özdemir

Ö. Özdemir has received his B.S. and M.S. from Middle East Technical University and Carnegie Mellon University in 2012 and 2014, respectively, all in Electrical and Electronics Engineering. He is with Acoustic Systems System Engineering Department of ASELSAN since 2015.

Osman Yalçınkaya

• O. Yalçınkaya has received his B.S. from Bilkent

University in 2017 in Mechanical Engineering. He is with Mechanical Engineering Department of ASELSAN since 2019.

Kerim Çepni

• K. Çepni has received his B.S. and M.S. from METU in

2009 and 2011, respectively, both in Mechanical

• Engineering. He is with Mechanical Engineering

Department of ASELSAN since 2012.

Aykut Şahin

• A. Şahin has received his B.S. and M.S. from Bilkent

University in 2006 and 2009, respectively, both in Electrical and Electronics Engineering. He is with Acoustic Systems System Engineering Department of ASELSAN since 2006.