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Odyssey IV

Odyssey IV. Principal Investigator C. Chryssostomidis F. Hover Design Team R. Damus S. Desset F. Hover J. Morash V. Polidoro. Table. Motivations – Needs– Missions Data Product Lessons From Previous AUVs Mechanical Propulsion Dynamics Electrical Payload Software

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Odyssey IV

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  1. Odyssey IV Principal Investigator C. Chryssostomidis F. Hover Design Team R. Damus S. Desset F. Hover J. Morash V. Polidoro

  2. Table • Motivations – Needs– Missions • Data Product • Lessons From Previous AUVs • Mechanical • Propulsion • Dynamics • Electrical • Payload • Software • Schedule and Cost Estimates

  3. – Motivations – Needs – Missions Rob

  4. Rationale for an Odyssey IV AUV Class • National Research Council “Future Needs in Deep Submergence Science”, 2004 • US $25M to replace Alvin and upgrade ROV fleet Goal: Put humans deeper to leverage in-situ decision-making No money for AUVs  SG to promote AUV involvement with a true deep-water platform that is cheap and can sample disparate locales quickly and return high resolution data products for site characterization prior to HOV deployment • Benthic Community Genomic Relationships (WHOI “Oceanus” 2004) • WHOI sponsored research identifies species Goal: Understand origin of species by sequencing DNA An AUV with large payload capacity can carry novel sensors to collect samples • Cold Water Coral Reefs • Chemosynthetic life-cycle is poorly understood Goal: Improve database of knowledge about this cycle and ecological linkages Hover capable AUV can investigate areas where feature relative navigation is desirable option to probe deep water coral Rob

  5. Odyssey IV Concept Focus Areas • A low-cost, reconfigurable, 3000m “truck” • Short missions – choose many quick, surface-deployed sampling missions rather than long surveys • Restricted data products, e.g., a single geo-referenced touch-down location, a small photographic survey, a single non-specific sample of the benthic surface, etc. • Focus on deployment of multiple vehicles without requiring continuous navigation of each vehicle. Rob

  6. 0 1 2 3 4 Missions and Relative Mission Difficulty Power consumption not including thrusters One geo-referenced point (GRP) at seabed <50 W (pinger, MEH and core sensors) Visual survey relative to initial GRP ~250 W (plus camera/lights) Go to a given GRP and do visual survey ~300 W (plus DVL) … and get any sample … and get a targeted sample ~800 W (plus sampling device) Rob

  7. Power consumption (including thrusters) ConOps ~84 Wh • Get to depth quickly • V = sqrt( 2*(W – B ) / CD ) ~ 3.0 m/s • requires 30kg dropweight • 3km  16.67min (@ 60deg pitch, 34min) • Survey small area • O( 200m X 200m X 10m spacing) @ 1m/s • coverage overlap: 50% • 73.3min • Rise to surface • Powered Ascent @ 1.5 m/s • 3km  33.33min • Recover from water • Transit to vehicle, hoist onto deck • 30min • Offload Data • 2200 images @ 3MB/img ~ 6.6GB data @ 100 Mbps • 10.26min • Total Time: ~3 hrs (163.56min - 180.56min) • Transit to new locale ~430 Wh ~100 Wh ~25 Wh ~9 Wh Total ~650Wh

  8. Needs – Sum Up • Good Maneuverability (4 DOF) • Stability (pitch and roll) • Quick inspection ~2 hour mission time • Fast dive and ascent streamlined body • Maximize bottom time dive time O(30 minutes) • Minimize turn around time ~1 hour on deck • Low cost ~$100,000 • Big Payload 50 kg reserve buoyancy Rob

  9. Data Products Jim

  10. Mission 2 – Data Products (1) • High resolution digital imaging • Easy to interpret • Spatial resolution ~ 1 mm • Range limited by water quality Sample image data, first-generation AUV LAB camera system Jim

  11. Mission 2 – Data Products (2) • High resolution digital imaging • Ultimate goal: 3-D reconstruction with photomosaic (future work) “Skerki D” sample photomosaic property of WHOI DSL Jim

  12. Mission 2 – Data Products (3) • High resolution acoustic imaging • More difficult to interpret • Range less limited by water quantity • Spatial resolution ~ 1 mm MS 1000 Kongsberg Data from “Royal Navy” Jim

  13. Mission 2 – Data Products (4) • Sample Return • A future research direction, once the base vehicle is complete • Possible subsystems range from simple water pumps to hydraulic jackhammers and manipulators • Scientific interest in organisms and chemicals from midwater, seafloor sediments, hydrothermal vents and coral reefs • Demands increased vehicle intelligence Jim

  14. Mission 2 – Data Products (5) • Sample Return • Sampling subsystem concepts Harbor Branch suction sampler Schilling Robotics ORION manipulator Stanley hydraulic chipping hammer Jim

  15. Lessons From Previous AUVs Vic

  16. Previous Experience (1) • What we’ve learned from previous experiences : • How to hover and maneuver at low speeds • Take advantage of a large hydrostatic righting moment • Try to put the thrusters along an axis of symmetry • Minimize the coupling between axes • Preserve a streamlined direction Vic

  17. Previous Experience (2) Hovering AUV Projects at other institutions ABE ALISTAR 3000 SAUVIM ALIVE SENTRY (not hovering) SeaBED Vic

  18. Mechanical Layout Sam

  19. Mechanical – Design Evolution Sam

  20. Mechanical - Layout (1) Sam

  21. Mechanical - Layout (2) Sam

  22. Mechanical - Layout (3) Sam

  23. Mechanical - Layout (4) Sam

  24. Mechanical – Thrusters function Sway and Yaw Heave and Surge Sam

  25. Mechanical – Devices Layout Sam

  26. Mechanical – Devices Layout Foam Actuation housing MEH Batteries Payload Bay Sam

  27. Mechanical – Structure Vic

  28. Mechanical – Drop Weight Mechanism Vic

  29. Mechanical – Rotating Thruster Assembly Sam

  30. Mechanical – Foam • Off the shelf blocks of foam ($1000/f3) 1’x6”x2’ 1’x6”x1.5’ 1’x6”x1’ 1’x6”x0.5’ Sam

  31. Mechanical – Weight Repartition (~350Kg) Sam

  32. Propulsion The following analysts are based on Bollard thrust from manufacturer and projected surface area Sam

  33. Mechanical – Thruster manufacturer Regression based on manufacturer data (bollard thrust) Sam

  34. Mechanical – Thrusters chosen Deep Sea System 1HP Bollard Thrust Sam

  35. Mechanical – How many thruster per axis? Bollard curve Sam

  36. Mechanical – How fast can we? Surge Sam

  37. Mechanical – How fast can we? Sway Sam

  38. Mechanical – How fast can we? Heave Sam

  39. Mechanical – How fast do we go down? (1) Propulsion Sam

  40. Mechanical – How fast do we go down? (2) Cd=0.4 Cd=0.1 Descent Weight Pitch + Thrust Total Force Speed Sam

  41. Dynamics Vic

  42. Dynamics – Vectored Thrust Control Problem (1) • The essential system is described by Mx’’(t) = F(t) cos q(t) Mz’’(t) = F(t) sin q(t) where x(t) is surge position z(t) is heave position F(t) is thrust level q(t) is pitch of the thruster • Pitch is subject to velocity and acceleration limits, and may be limited to 360 degrees of rotation • Thrust is subject to bandwidth limits Vic

  43. Dynamics – Vectored Thrust Control Problem (2) • In a steady disturbance, such as forward flight or a buoyancy force, the control inputs can be effectively linearized, giving excellent vectored thrust control • When pure hovering is needed, the system cannot be stabilized to zero, except in the limiting case of zero closed-loop bandwidth. • This is an extremely active area of research in the dynamic positioning community, usually with multiple thrusters. Vic

  44. Dynamics – Rotating Thruster (1) Cruising + Low Frequency Disturbances Vic

  45. Dynamics – Rotating Thruster (2) Cruising + High Frequency Disturbances Vic

  46. Dynamics – Rotating Thruster (3) Hovering + Low Frequency Disturbances Vic

  47. Dynamics – Rotating Thruster (4) Hovering + Low Frequency Disturbances Vic

  48. Dynamics – Rotating Thruster (5) Hovering + High Frequency Disturbances Vic

  49. Dynamics – Rotating Thruster (6) Hovering + High Frequency Disturbances Vic

  50. Potential difficulties with nonlinear approaches: unexpected behavior, unrealistic demands on physical system, instability, etc. Very few tools available for design; analysis is by simulation. Pursue a linear approach to hovering; this requires regularization of pitch angle - i.e. regular, synchronized motion. One approach: rotate the pitch servo at constant rate (q). This partitions thrust into four quadrants per turn - two used for heave DOF and two for surge DOF. T T/4 T/2 3T/4 Because thrust in each DOF is available on a regular time base, classical discrete-time control principles can be used; the two DOF are actuated alternately. The available positioning bandwidth is closely related to q and to the time scales of thrust production during a rapid turn. Linear approach allows systematic design.

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