Advantages of a combined sonar data acquisition system for AUVs and ASVs
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The document outlines the advantages of the Edgetech 2205 sonar system for Autonomous Underwater Vehicles (AUVs) and Autonomous Surface Vessels (ASVs), which allows for combined data acquisition of various sonar types. It details the system's capabilities, including dual or triple-frequency side scan sonar, multiphase echosounder bathymetry, and sub-bottom profiling, as well as its modular and configurable design for different survey missions. The integration of these advanced sonar technologies facilitates high-resolution underwater surveys and inspections in challenging environments.
Advantages of a combined sonar data acquisition system for AUVs and ASVs
- 1. Advantages of a combined sonar data acquisition system for AUVs and ASVs Tom Hiller tom.hiller@edgetech.com
- 2. Abstract: • Autonomous underwater vehicles (AUVs) often operate close to the seabed (5m-15m) enabling higher resolution surveys using high frequency sonars. Compact Autonomous surface vessels (ASVs) are often deployed in shallow water environments where deeper-draft manned survey vessels are unable to operate. On such vehicles there is limited space to deploy separate imaging, mapping and sub-bottom sonars. This presentation describes the technology deployed in the EdgeTech 2205 sonar system, which enables combined data acquisition in one system on AUVs and ASVs. Examples of the data acquired are given, which can include dual- or triple- frequency side scan, Multiphase Echosounder (MPES) swath bathymetry, and sub-bottom profiler data.
- 3. There are 4 factors that make a successful Unmanned Vehicle: The Vehicle Positioning Data Acquisition Control
- 4. What does an autonomous vehicle do? The AUV/ASV must: • Be able to carry out a mission plan • Be able to position itself accurately and reliably • Collect useful data A lot of development effort has gone into the vehicle and control Positioning is a whole other presentation The point of having the system in the field is to collect data
- 5. • Industry leader in Underwater Acoustics • EdgeTech (formerly EG&G Marine Instruments) – Started in 1966 by Doc Edgerton • ORE Offshore – Formed in 1963 • Manufacturing and Support - Massachusetts USA • R&D – Florida USA • + Worldwide rep network and regional Authorised Service Centres EdgeTech Background Common Technologies Underwater Acoustics Digital Signal Processing
- 6. • Sonar Systems – Side Scan Sonar – Sub-bottom Profilers – Bathymetry – Combined Systems – AUV/ROV Systems • Actuated Products – Acoustic Releases – Pop-up Systems – Acoustic Actuators • Navigation & Positioning – USBL Acoustic Tracking Systems – Motion Reference Unit (MRU) EdgeTech Products & Solutions
- 7. • A Modular and Configurable Sonar System for Hosted Platforms • For installation on Unmanned Underwater Vehicles (UUVs / AUV), Remotely Operated Vehicles (ROVs), Unmanned Surface Vehicles (USVs), and other hosted platforms. • Modular units able to be configured, based on the application, to collect side scan sonar imagery, sub-bottom profiler data and wide swath bathymetry data, singly or in concert with one another. Designing Data collection for AUVs and ASVs
- 8. • Stage 1 Introduced 1st Qtr 2013 – Dual frequency side scan • Option for Dynamic focused capability : 230 / 850 DF one of the first frequency sets – Sub-bottom capability with linear amplifier card • Various transmit / receive array options • Stage 2 Completed 2014 – Bathymetry capability • Needs an additional board (24 ch A/D) • Needs bathymetry capable arrays – Tri-Frequency side scan • Can run dual simultaneous side scan, where the operator can choose any two frequencies from the three available As of end 2015 over 50 types of unmanned vehicles have integrated EdgeTech sonars 2205 Development:
- 9. • Side Scan – Single or dual frequency Arrays – Dynamic Aperture / Dynamic Focussing options • Sub-bottom Profiler – Range of frequencies / Transducer Options • Swath Bathymetry – Multiphase Echosounder wide swath bathymetry Combinations of frequency options to suit the application 2205 Options
- 10. Configuration 1 – SSS / Bathymetry only SSS / Bathy Port Array Starboard Array AUV control/ ROV Mux
- 11. Sub-Bottom Configuration 2 – SSS / Bathymetry / SBP SSS / Bathy Port Array Starboard Array AUV control/ ROV Mux Hydrophones Hydrophones Tx Tx
- 12. 2205 Board Set Building Blocks PSU CPU SAIBU Cap Banks SIM (blue board) HCCA (bathymetry only) Board Stack Weight in Air with Cabling = ~3.2lbs
- 13. Size – Housing for SSS / SBP / Bathymetry
- 14. • Ethernet – Data out – Navigation data in – Command and Control • Backward compatible with existing EdgeTech Interface • RS232 – 2 low latency ports as standard – Navigation and motion data in • Triggers – 3 configurable as in / out – Typically configured as trigger in, PPS in, and Trigger out • Expansion capability – 2 x USB 2.0 ports – SATA interface for onboard storage Standard Interfaces
- 15. JSF File Format • May contain the following (depending on what sensors are configured/installed): – Dual Frequency SS – Bathymetry – Sub Bottom – Navigation (lat/lon) – Attitude (roll/pitch/heave) – Heading – Pressure (or Depth) – All with a common time stamp A Common, Standardised File Format
- 17. ASV Deployment Examples : ECA Inspector • Side Scan / Bathymetry system • Automated Bow mount
- 18. ASV deployment example: swath bathymetry + dual frequency side scan
- 19. C&C / ASV 6300 • Side scan sonar • Sub-bottom Profiler • Hull mounted systems Deployment examples :
- 20. ASV example : Sea Robotics • Side Scan Sonar • Sub-Bottom Profiler
- 21. AUV / ROV Systems
- 22. 2205 Example Configurations Application Sensor Frequencies Survey Goals & Considerations Military MCM Side Scan only 540/1600 kHz High resolution small size target location and identification. 230/850DF kHz Highest resolution-to-range on a standard military COTS side scan sonar Side Scan + Bathymetry 540/1600 kHz with Bathymetry at 540kHz High resolution small size target location and identification that has bathymetry for added 3D verification. Commercial Survey (small vehicle 4-9”) Side Scan only 410/850 kHz Maximum range-to-resolution package for a small auv 540/1600 kHz Higher resolution survey solution for small auv with added Bathymetry capability Side Scan + Bathymetry 540/1600 kHz (bathy on 540 kHz) Higher resolution survey solution for small auv Commercial Survey (large vehicle 10”+) Side Scan only 120/410 kHz Maximum range surveying on a large vehicle. 230/540 kHz Best mid-range compromise between range/resolution for surveying 230/850DF High res on a large auv. DF for extra focus on small targets 230/540/1600 kHz Tri-Frequency Any two frequencies at the same time, with the selection optimized for the mission Side Scan + Bathymetry 230/540 kHz (bathy on 540 kHz) Best mid-range compromise with added Bathymetry 230/540/1600 kHz (bathy on 540 kHz) Tri-Frequency (any two side scan frequencies at the same time) , with bathymetry also available if 540 kHz is selected as one of the frequencies Sub-bottom Profiler (Optional) 4-24 kHz Smallest size, highest resolution, but least penetration 2-16 kHz Good balance between size and performance (penetration & resolution) 1-8 kHz Best penetration, largest size and power consumption
- 23. Technology Details • Side scan • Sub bottom • Bathymetry
- 24. • Sideways looking ; 2 sides • Wide vertical beam • Narrow horizontal beam 2205 : Side Scan Sonar • The sonar sends out sound pulses or pings from each side of the tow fish and then receives or listens for the pulse to return. • Each ping returns a line of imagery. These pings are combined together to create an image.
- 25. 2205 : Side Scan Frequencies Chirp Centre Frequency Nominal Frequency* Range 120 kHz 100 kHz 250 to 500m 230 kHz 300 kHz 150 to 300m 410 kHz 400 kHz 130 to >200m 540 kHz 600 kHz 100 to 150m 850 kHz 900 kHz 50 to 75m 1600 kHz 1600 kHz 20 to 35m You will sometimes see the ‘nominal’ frequency quoted in specifications and marketing material. The selection of the best side scan sonar frequency for any application is a compromise between range and resolution. Lower frequency systems provide longer range (allowing a larger area to be covered in each pass), whilst higher frequency systems provide a higher definition image
- 26. • Standard or Customised Arrays – Standard arrays from towed systems – Customised arrays for a particular vehicle • Rear radius to fit vehicle • Different connection options • Dual Frequency Combinations – Lower frequency provides a search capability – Higher frequency provides classification / identification – Typical Combinations: • 120 / 410 kHz • 230 / 540 kHz • 230 / 850 kHz • 400 / 900 kHz • 600 / 1600 kHz • Tri-Frequency – Operator selects two from three – Selection depends on mission – Typical Combinations: • 230 / 540 / 850 kHz • 230 / 540 / 1600 khz Dual Frequency or Tri-Frequency Side Scan
- 27. Dynamic Focussing : Results 300 kHz 8 Element Dynamic Focusing300 kHz No Dynamic Focusing • Various configurations have been built – Different Frequencies – Different number of segments – Variable length segments – Not necessarily symmetrical
- 28. • Range of SBP Transducer Options 2205: Sub-bottom Profiler DW-424 DW-216 DW-106 Frequency Range 4 – 24 kHz 2 – 16 kHz 1 – 8 kHz Pulse Type Full Spectrum chirp frequency modulated pulse with amplitude and phase weighting Vertical Resolution (depends on Pulse selected) 4 – 8 cm 6 – 10 cm 15 – 25 cm Penetration (typical) In coarse calcareous sand In clay 2 m 40 m 6 m 80 m 15 m 150 m Beam Width (depends on centre frequency) 15° - 25° 15° - 25° 28° - 36°
- 29. • EdgeTech “Full Spectrum” pulse characteristics – Bandwidth • The wider the bandwidth, the better the resolution – Length • Longer pulses provide more acoustic energy – Waveform • For “FM” shaped pulses the Full Spectrum wavelet is weighted in the frequency domain to have a Gaussian like shape (Blackman-Harris window) which provides a great rejection of the side lobes. • Wideband (WB) pulses have a flat response over the entire pulse bandwidth, so more low frequency content. • Sweep has a linear variation of frequency with time. • Quadratic Pulses – Waveform • Sweep rate varies with time, with greater proportion of pulse length spent at lower part of the frequency range. • Designed to help improve penetration. • Dual Frequency Mode – Two data streams • Two data streams, each utilising a different pulse. Sub-bottom Profiler Pulse Options
- 30. • Transmit and Receive on the Transducer – Reduced Hardware • Adds a T/R (Transmit/Receive) switch, but removes the need for separate receive hydrophones. – Limits Pulse Length • Limits the pulse length that can be used when close to the seabed – need to stop transmit pulse, and eliminate ringing, before 1st receive. • Not recommended for AUV’s. • Separate PZT receive Hydrophone arrays – Pulse length independent of altitude • Can receive on hydrophones whilst still transmitting. – Linear arrays in parallel used to define receive beam pattern • Separate PVDF receive Hydrophone panels – Pulse length independent of altitude • Can receive on hydrophones whilst still transmitting. – Standard panel sizes or Custom built • Custom sizes can be designed to fit vehicle • Multiple receive options for different applications. Sub-bottom Profiler Receive Options
- 31. Sub-bottom Profiler on an AUV AUV Sub-Bottom data DW-106 Transmit Quadratic pulse PVDF receive arrays
- 32. Applications : Pipeline and cable detection
- 33. 2205 Bathymetry Technology • Multi-Phase Echo Sounder (MPES) technology (same as EdgeTech 6205) • Swath up to 10 x water depth, and IHO SO to up to 9 x water depth. • Two Bathymetric frequency Options – 230 kHz, longer range – 540 kHz, higher resolution • Integrated Dual Frequency Side Scan • Better Spatial Resolution, but without the Nadir gap traditionally associated with Interferometers Typical Multibeam Footprint Typical 6205 Footprint
- 34. 2205 Bathymetry: Frequency Options • The 6205 is available in several standard frequency configurations: – 230 kHz Bathymetry : to 215m depth below transducers With 230 & 550 kHz Dual Frequency Side Scan – 550 kHz Bathymetry :to 75m depth below transducers With 230 & 550 kHz Dual Frequency Side Scan – 550 kHz Bathymetry With 550 & 1600 kHz Dual Frequency Side Scan The modular design of the 6205 also allows for multi-frequency bathymetry options with field exchangeable array design for survey operations in both shallow and deep water operations.
- 35. Data Examples
- 36. 6205 Performance across swath-Data Example Data Resolution retained across swath Cross Section Shown
- 37. 1600kHz SS Data Sample, 5m Altitude
- 38. 1600kHz Data Sample, MLO
- 39. 1600kHz Data Sample, MLO
- 40. • Bathymetry & Simultaneous Dual Frequency Side Scan Sonar • Precisely Co-Registered Bathymetry & Side Scan Imagery Co-Registered Bathymetry & Side Scan
- 41. 550kHz SS Data Sample, 12m Altitude
- 43. High-Density Cloud View of Processed Bathymetry Sand Waves Swath Bathymetry with Side Scan
- 44. Co-Registered Bathymetry & Side Scan
- 45. Co-Registered Bathymetry & Side Scan Nadir Coverage
- 46. Data: Examples
- 47. Data: Examples
- 48. Swath Bathymetry : Pipeline Data Example
- 50. Eel Grass in Side Scan & Co-Registered Bathymetry Water Depth less than 1 meter at Chart Datum
- 51. Side Scan and Bathymetry : AUV Data At this resolution, the Bathymetry data quality is limited by the quality of the motion data.
- 52. AUV Swath Bathymetry with Co-registered Side Scan The Great Lakes Research Center (GLRC) at Michigan Technological University, deployed an OceanServer Iver AUV with an EdgeTech 2205 combined Side Scan Sonar and Bathymetry system with the goal of imaging an underwater pipeline. Side scan sonar and bathymetry images were used to check the location and integrity of the pipeline over a long and varied terrain. Using side scan sonar co- registered with bathymetry the team was able to view intricate details about the pipeline and the bottom topography, helping accomplish their mission.
- 53. Conclusion • Flexible and configurable sonar data collection via the EdgeTech 2205 sonar system now enables AUV and ASV technology to carry out a variety of offshore survey, search and inspection tasks.
- 54. Advantages of a combined sonar data acquisition system for AUVs and ASVs Tom Hiller tom.hiller@edgetech.com