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3-dimensional forward-looking Imaging Sonar for Autonomous Underwater Vehicles

Primary Information

Domain

Security & Defence

Project No.

4382

Sanction and Project Initiation

Sanction No: From MHRD: 3-18/2015-T.S.-I (Vol. IV)

Sanction Date: 17/05/2017

Project Initiation date: 30/08/2017

Project Duration: 36

Partner Ministry/Agency/Industry

DRDO; Larsen & Toubro Limited, Mumbai

 

Role of partner:L&T shall contribute in the following activities for this joint development project: a. Provide the indigenous AUV platform for housing, testing and deploying the Imaging Sonar. b. Develop electronics processing hardware and packaging of the complete Sonar system. c. Interface the Sonar system with the rest of the AUV platform. d. Provide engineering manpower for software and algorithm implementation.

 

Support from partner:L&T shall provide the following support: i) off-shore facility for testing of the prototype Imaging Sonar in stand-alone and AUV integrated modes, ii) engineering manpower for software and algorithm implementation, iii) indigenously developed AUV platform for integrating the Imaging Sonar and testing it, iv) packaging of complete Sonar system, and developing electronics processing hardware.

Principal Investigator

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Prof Arun Kumar
IIT Delhi

Host Institute

Co-PIs

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Prof. R. Bahl
IIT Delhi

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Dr. Prabhu Babu
IIT Delhi

 

Scope and Objectives

Autonomous Underwater Vehicles (AUVs) can operate at great depths and in hostile environments that may pose obstacles in their path. Underwater cameras do not perform well, and can at most provide images up to few meters depending on turbidity. Imaging Sonars can provide images even in turbid water for several hundred meters. Underwater scenarios can be better understood by 3D-capable Imaging Sonars over much larger distances than is possible with cameras. With the advent of AUVs, there is a strong need to deploy intelligent Imaging Sonar for autonomous operations. An indigenous capability in system-level development is imperative for customization of the system for specific mission requirements, and doing experimental research. The scope of this project is to design and develop a 3D forward looking prototype Imaging Sonar that shall be tested firstly in the tank facility at IIT Delhi, and then in field tests at Larsen & Toubro's offshore test facility.The Sonar shall be integrated with Larsen & Toubro's AUV platform which shall provide a platform to design and test novel signal processing algorithms. The Sonar design shall explore optimal planar array designs in terms of number of sensor element requirements, novel waveform designs and compressive sensing techniques to reduce hardware complexity while retaining the high-resolution image specifications.

Deliverables

Final Outcome: Working prototype 3D Imaging Sonar with given specifications and tested in the laboratory and field shall be the final outcome of the project. Deliverables: 1. Working prototype 3D Imaging Sonar with given specifications and tested in the laboratory and field. A block diagram representation of its components is shown. 2. Project Report encompassing research outcome in terms of novel design aspects of the imaging sonar hardware, optimal planar array designs in terms of number of sensor element requirements, novel waveform designs and compressive sensing techniques to reduce hardware complexity while retaining the high-resolution image specifications. 3. 3D Imaging Sonar System Design Document of its hardware and associated software and User Manual.

 

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Scientific Output

The following additional progress was made since the previous report: 1. Multi-channel Digital-to-Analog Converter Design and Realization: Progress made till date for testing at sub-system level of compact multichannel Digital-to-Analog Converter module for 128 channels and 3 MHz per channel rate: a) A 4-channel version of the 128 Digital-to-Analog Converter module has been designed and fabricated for testing in the lab. b) Algorithms for configuring, storing coded waveforms and continuous transmission using the module has been worked out. 2. Study of Target Echo characteristics in Underwater Tank: Several experiments were performed in underwater tank facility to study the effect of target surface roughness on its echo characteristics for different targets. Target was placed between a wall of the tank and transmitter-receiver direct line of sight. The target was then rotated 360 degrees in small increments of 10 degrees and its surface is insonified with transmitted sinusoid signals with frequencies in 130 to 170 kHz. The object whose surface is more rough presented a more uniform distribution of energy as function of the angle. 3. Low Noise Pre-Amplifier Design (2nd version with low spatial volume requirement for AUV): In view of the large volume and precision fabrication requirements of the 1st version of the low-noise preamplifier design, we have designed a more compact pre-amplifier for use with the multi-channel hydrophone array, to be placed in AUV platform. This pre-amplifier has two stages of gain. The first one is Low Gain with multiple parallel configuration which gives ultra-low Noise (referred to input) while the second stage gives high Gain (60 dB) with configured bandpass filter. 4. Sequence set design has been undertake with newer method of Majorization-Minimization (MM) on exact objective function. This leads to a drastic reduction on sequence design time compared to previous method of using SCAN algorithm. We are using the MM approach to design code sequences that improve upon the auto-correlation and cross-correlation properties.

 

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Results and outcome till date

The following progress was made since the previous report:
1. Multi-channel Digital-to-Analog Converter Design and Realization for 4-channels at 3 MHz per channel rate. It is now being realized for 128 channels.
2. Algorithms for configuring, storing coded waveforms and continuous transmission have been tested.
3. Study of Target Echo characteristics in Underwater Tank completed in underwater tank facility to study the effect of target surface roughness on its echo characteristics for different targets at 130-170 KHz.
4. Ultra-low Noise Pre-Amplifier Demodulator Design and Testing completed. Fabrication for 128 channels is in progress.
5. Sequence set design done with newer method of Majorization-Minimization (MM) on exact objective function completed. This leads to a drastic reduction on sequence design time compared to previous method of using SCAN algorithm. We are using the MM approach to design code sequences that improve upon the auto-correlation and cross-correlation properties.
6. Realization of complete stand-along Sonar System for field test is in progress.

 

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Societal benefit and impact anticipated

Acoustic imaging systems are useful for inspecting or examining underwater objects because water turbidity does not mostly allow the use of underwater cameras or other optical means of viewing. Most ocean waters are turbid and visibility varies between about ten meters in deep ocean water (undisturbed) to 1 to 6 m in near-shore waters and 0 to 1 m within harbours and estuaries. As acoustic energy propagates longer distances and more easily penetrates mud and silt that are responsible for optical turbidity, it allows an Imaging Sonar to provide scene information for longer ranges of the order of 100 m, while providing comparable resolution with higher frequencies, apertures and novel system designs. AUVs are the natural platforms to integrate the 3D acoustic Imaging Sonars with. Their integration on AUV platform will significantly enhance the capability of underwater exploration for diverse applications. Further, the integration of indigenously developed 3D Imaging Sonar on an indigenously developed AUV platform will greatly enhance the indigenous capability in this important emerging field of activity. Potential users of this capability include: 1. Ship building corporations for underwater inspection and maintenance of ships hull, 2. Military for imaging and obstacle avoidance with AUVs, port and harbour monitoring and reconnaissance, 3. Oil and Natural Gas Corporation, for offshore site surveys and inspection, and monitoring of silt and debris deposition under rig platforms, 4. Dam Authorities and Inland Waterways Authority for monitoring of structures, maintenance tasks etc.

Next steps

The Sonar design has been completed. Hardware and software modules are currently being implemented for realization of the prototype system and hardware components are under purchase process. Testing at sub-system level of the different modules of the hardware has been initiated. It is expected that the complete prototype system shall be ready for lab testing at the IIT Delhi Underwater tank facility. This will be followed by testing at the NIOT Chennai Underwater tank facility in 6 to 8 months. Further, we will undertake field testing at Larsen and Toubro's offshore facility near Chennai.

Publications and reports

1. A. Goel, A. Kumar and R. Bahl, "Steerable sparse linear array synthesis based on multiple measurements vectors compressive sensing method," The Journal of Acoustical Society of America, vol. 145, no. 3, pp. 1212-1220, 2019.
2. A. Goel, A. Kumar and R. Bahl, "Steerable sparse linear array synthesis using second order cone programming," 2019 IEEE Symposium on Underwater Technology, Taiwan, April 2019.

Patents

1. Arun Kumar, Rajendar Bahl, Prabhu Babu, Nidhi Bisla, Surya Prakash Sankuru, " Three-dimensional imaging sonar with linear transmitter and receiver arrays," Indian provisional patent no. 201911031284, Applied.

Scholars and Project Staff

Research Scholars: 1. Nidhi Bisla (January 2018 onwards) 2. Arun Goel (January 2018 onwards) 3. Surya Prakash (January 2018 onwards). Project Scientists: 1. Sandhya Prajapati (January 2018 onwards). 2. Richa Agarwal (November 2017 to Jan 2018). 3. Ratnesh Pandey (April 2018 onwards). Project Assistant: 1. Vikas Mishra (November 2017 onwards). Project Contractual appointments: 1. Bharat Agarwal (March 2018 to September 2018). 2. Rahul Nishad (April 2018 to October 2018). 3. Netra Lal Ghimre (November 2017 to April 2018). 4. Shadab Anwar (August 2018 onwards).

Challenges faced

We have faced difficulty in getting a manufacturer to fabricate the sophisticated sonar arrays (transmitter & receiver) according to our design. Another difficulty is the long lead time of about 6 months being quoted to supply the manufactured array. However, in this case, it also requires us to develop ourselves the corresponding 128-channel power amplifier for the transmitter array and 128-channel low noise pre-amplifier for the receiver array.

Financial Information

  • Total sanction: Rs. 34200000

  • Amount received: Rs. 20050000

  • Amount utilised for Equipment: Rs. 6104548

  • Amount utilised for Manpower: Rs. 3487556

  • Amount utilised for Consumables: Rs. 3300292

  • Amount utilised for Contingency: Rs. 126628

  • Amount utilised for Travel: Rs. 53611

  • Amount utilised for Other Expenses: 0

  • Amount utilised for Overheads: Rs. 3341000

Equipment and facilities

 

Multi-channel data acquisition system, Hydrophones, Single board computer system in PC-104 format, Mixed signal oscilloscopes, 64-channel ADC boards for sampling up to 200 KSPS per channel (2 nos), High-speed Multi-channel Digital I/O boards, FPGA kit.

Additional equipment purchased: 1) Data Logging & Acquisition digital I/O PCI card.