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FSN WP5: Go To Formation
Andreas J. Häusler, IST
An Aspect of Multiple Marine Vehicle Path Planning
Mission Planning
• Multiple vehicle missions require the vehicles to be in formation
• An initial formation has to be established before the mission starts
• Vehicles cannot be deployed in formationNeed to get the vehicles into initial formation
Path Generation’s General Problem
• Problem description– Desired waypoints or manoeuvres– Desired AUV formation– Optimal energy expenditure or manoeuvring time
Path Generation’s General Problem
• Difficulties– Go-to-formation manoeuvre (collision-free paths)– Avoid (concave, static) obstacles– Opt. 1 – Generate non-intersecting paths– Opt. 2 – Allow for intersecting, “time-coordinated”
trajectories– Meet energy and trajectory
constraints
Path Generation• Avoid absolute timing (to cope with disturbances)• Reaching the target positions simultaneously will
ensure the required initial formation.
Decouple spatial and temporal constraints!
Step 1. Produce paths p(t) without explicit time constraints (polynomial function of t)
Step 2. Establish a timing law for = (t t t) (polynomial)τ)
Inspired by the work of Isaac Kaminer and Reza Ghabcheloo
Path Generation
Decouple spatial and temporal constraints!
• To translate between t and τ use
(adopt a polynomial approach to ( )h t )
Step 3. Use an optimization of your choice for criterion minimization.
Inspired by the work of Isaac Kaminer and Reza Ghabcheloo
Path Generation
• Polynomial equation
• Taken for all DOFs (extremely simple system!)
Inspired by the work of Oleg Yakimenko, NPS, USA
Multiple Vehicle Manoeuvres
• Most vehicles are underactuated and lack hovering capabilities
No station keeping at deployment time, no station keeping after vehicles reach mission starting positions
Mission has to start on-the-fly
• Vehicles should automatically be driven from deployment to mission start
Go To Formation• 1st part of the overall manoeuvre
• Needs to take into account initial deployment positions and orientations
• Needs to ensure simultaneous arrival at designated positions and orientations
Go To Formation• Needs to avoid collisions until mission
control takes over• Needs to consider
time, energy and vehicle constraints
• Method has been extended to deal with intersecting paths.
Go To Formation• How do we deal with “deviations from the
plan? (wind, currents, etc.)• Use cooperative
path following! (methods are available - IST, NTNU)
The Grex 2008 Azores Mission
• July 2008 in Horta, Faial (Açores)• 5 Nations, 9 Institutions
• Successful sea trials of Coordinated Path Following and Coordinated Target Tracking
Coordination and Control of
Cooperating Heterogeneous Unmanned Systems
in Uncertain Environments
The Grex 2008 Azores Mission
• The GREX System provides– Central planning for teams– Hardware/OS Abstraction– Information and command flow accross multiple
vehicles– Central and distributed mission planning– Complex coordination capability– Safety checks at several levels, transmitted via
status/emergency telegrams
The Grex Vehicle Architecture
The Grex 2008 Azores Mission
Simple Path Following• Desired Path is predefined• DELFIMX follows a
mission consisting of predefined #ARC and #POINT (line) SVPs
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The Grex 2008 Azores Mission
Coordinated Path Following• Path already
provided• Vehicles
coordinate with leader vehicle to do coordinated path-following
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The Grex 2008 Azores Mission
GoToFormation• MVP implementation
to take vehicles to a starting formation
• Will use path/trajectory planning algorithms that do spatio-temporal deconfliction
• Obstacle avoidance is also required
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The Grex 2008 Azores Mission
Simple Target Tracking• Águas Vivas
moves around while sending DELFIMX its GPS locations
• DELFIMX estimates path followed in GREX SVMP format and follows this path
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The Grex 2008 Azores Mission
Coordinated Target TrackingDELFIMX GREX-module’s estimator learns path of Águas Vivas and does a coordinated path-following with Seabee AUV using GREX MVPs
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The Grex 2008 Azores Mission• Because GREX deals with multiple vehicles, a
Go-To-Formation behaviour is necessary for each mission
• My part in the mission:– Developed an algorithm for Go-To-Formation– Helped developing the software for telegram
processing (communication on the vehicle side)– Developed software to be ready to go to sea in
Sesimbra, September 2008
Grex 2008 Azores Mission: Results• Path Following
Grex 2008 Azores Mission: Results• Target Tracking
Future Work
1. Incorporate deconfliction in time
2. Go on to three-dimensional paths
3. Finally, think about on-line path planning
during mission runtime
Thank you for your attention!
AND NOW FOR A MOVIE…