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           . FREE sub NET. FSN WP5: Go To Formation. An Aspect of Multiple Marine Vehicle Path Planning. Andreas J. Häusler, IST. Mission Planning. Multiple vehicle missions require the vehicles to be in formation - PowerPoint PPT Presentation

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Slide 1

FREEsubNETFSN WP5: Go To FormationAndreas J. Husler, ISTAn Aspect of Multiple Marine Vehicle Path PlanningNo task number provided as IST is supposed to contribute to each part of WP 5Mission PlanningMultiple vehicle missions require the vehicles to be in formationAn initial formation has to be established before the mission startsVehicles cannot be deployed in formationNeed to get the vehicles into initial formationguas Vivasguas VivasPath Generations General ProblemProblem descriptionDesired waypoints or manoeuvresDesired AUV formationOptimal energy expenditure or manoeuvring time

What do we have to take into consideration?Path Generations General Problem

DifficultiesGo-to-formation manoeuvre (collision-free paths)Avoid (concave, static) obstaclesOpt. 1 Generate non-intersecting pathsOpt. 2 Allow for intersecting, time-coordinated trajectoriesMeet energy and trajectoryconstraints

What does our solution have to have?Difference between paths and trajectories.Path GenerationAvoid 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))

Inspired by the work of Isaac Kaminer and Reza Ghabcheloo

Path GenerationDecouple spatial and temporal constraints!

To translate between t and 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 GenerationPolynomial equation

Taken for all DOFs (extremely simple system!)

Inspired by the work of Oleg Yakimenko, NPS, USAThe coefficient matrix is achieved by writing the polynomial path for each degree of freedom (all required derivatives at all required points taken at the required , that is, the fraction of the path).

Now the path can be computed at each given by multiplying the polynomial coefficient vector (take the correct, i.e. 0th, 1st or 2nd derivative) with matrix A.Multiple Vehicle ManoeuvresMost vehicles are underactuated and lack hovering capabilitiesNo station keeping at deployment time, no station keeping after vehicles reach mission starting positionsMission has to start on-the-flyVehicles should automatically be driven from deployment to mission startGo To Formation

1st part of the overall manoeuvreNeeds to take into account initial deployment positions and orientationsNeeds to ensure simultaneous arrival at designated positions and orientationsThe vehicles also have to start at the same time; simultaneous arrival can only be done by different path lengths and/or velocities. This is simply due to the fact that we have the problem of no hovering capability. Therefore its impossible that some vehicles wait, because currents, waves, wind etc. will change their position and the calculated paths might not be correct anymore.Go To Formation

Needs to avoid collisions until mission control takes overNeeds 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 MissionJuly 2008 in Horta, Faial (Aores)

5 Nations, 9 InstitutionsSuccessful sea trials of Coordinated Path Following and Coordinated Target Tracking

Coordination and Control ofCooperating Heterogeneous Unmanned Systemsin Uncertain EnvironmentsThe Grex 2008 Azores MissionThe GREX System providesCentral planning for teamsHardware/OS AbstractionInformation and command flow accross multiple vehiclesCentral and distributed mission planningComplex coordination capabilitySafety checks at several levels, transmitted via status/emergency telegrams

We are trying to synergize and enable strong team-driven capabilities among teams of robotic vehicles with different abilities & architectures.

GREX will be a system that enables planning, communication, cooperative navigation, coordination and control of such vehicles from a seamless Team perspective.The Grex Vehicle Architecture

Two ways of communication among the vehicles:Data Telegrams (pre-defined data structures)General Telegrams

It is up to each client to decide if it wants to send synchronously or asynchronously.

A brief description of the modules:The main GREX computer generates SVMPs from the TMPCOM module is responsible for Inter-Vehicle communicationThe Team Handler on each GREX computer knows it is doing Coordinated Target Tracking or other tasks involving multiple vehiclesWe have a client-server architecture for IPC between GREX modulesThe GIM (GREX Interface Module) communicates information with the vehicle and also translates SVMPs to RVMPs (Real Vehicle Mission Plans)Team Navigation handles team-localization through info obtained through the COM client and GIM

Grex Team-Oriented Mission Planning

Mission Planning Software SeeTrack (by SeeByte)

MVP-PoolGREX Meta-language Team LevelGREX Meta-language Vehicle LevelLanguages of Real VehiclesGREXTeam Mission PlanMission Planningby OperatorMission Plan forVehicle 1Mission Plan forVehicle 2Mission Plan forVehicle nGREX Interface Module Veh.1GREX Interface Module Veh.2GREX Interface Module Veh.nto the vehiclesMission Plan forVehicle 1Mission Plan forVehicle 2Mission Plan forVehicle nTranslationby Mission Planning SoftwareRules,VocabularyMission Plan forVehicle n+1GREX Interface Module Veh.n+1Mission Plan forVehicle n+1new MVPsSlide from Thomas Glotzbach, COMPIT08

Grex Team-Oriented Mission PlanningSlide from Thomas Glotzbach, COMPIT08GREX ConsoleRunning SeeTrack

Translation Process

2. startVehicle Console

TMPSVMPSVMPSVMPSVMP4. CheckFormal Language VerificationSVMP3. Translation

SeeTrackSVMPSVMPSVMPTMP1. createOperator6. Translationinto Real Vehicle Languageby Vehicle ProviderRVMP7. CheckAlready existing checking processRVMPSVMP5. Transfer via Network LinkVehicleExisting HW

GREX HW

TMPSVMPRVMP8 . T r a n s f e r v i a N e t w o r k L i n k Grex Teamhandler Module

Slide from Thomas Glotzbach, COMPIT08MissionManagementManoeuvreManagementAutoPilotTeamHandlerMissionManagementManoeuvreManagementAutoPilotVehicle 3MissionManagementManoeuvreManagementAutoPilotVehicle 2MissionManagementManoeuvreManagementAutoPilotVehicle 1Manoeuvre Management: Mission Modification (Obstacle Avoidance) Mission Adjustment (Typical Primitive Execution)Mission Management: Mission Reorganisation (Handling of special situations) Auto Pilot (Team): Mission Coordination (keeping of formation, inter vehicle collision avoidance) The Grex 2008 Azores Mission

Simple Path FollowingDesired Path is predefinedDELFIMX follows a mission consisting of predefined #ARC and #POINT (line) SVPs

Slide from Arvind Pereira, USCThe Grex 2008 Azores Mission

Coordinated Path FollowingPath already providedVehicles coordinate with leader vehicle to do coordinated path-following

Slide from Arvind Pereira, USCThe Grex 2008 Azores Mission

GoToFormationMVP implementation to take vehicles to a starting formationWill use path/trajectory planning algorithms that do spatio-temporal deconflictionObstacle avoidance is also required

Slide from Arvind Pereira, USCThe Grex 2008 Azores Mission

Simple Target Trackingguas Vivas moves around while sending DELFIMX its GPS locationsDELFIMX estimates path followed in GREX SVMP format and follows this path

Slide from Arvind Pereira, USCThe Grex 2008 Azores Mission

Coordinated Target TrackingDELFIMX GREX-modules estimator learns path of guas Vivas and does a coordinated path-following with Seabee AUV using GREX MVPs

Slide from Arvind Pereira, USCExample of communication structureCollect tracking-data from Comm moduleFilter, smooth and estimate arc and straight line reference pathsDispatch one arc/line at a time via the radio to other Team Handlers by using the CHANGE_PARAMETER_OF_SUBMANEOUVRE_SVMP and CHANGE_PARAMETER_OF_PRIMITIVE_SVMP telegrams to vehicle Team handlersVehicle Team Handler may change mission parameters or change velocity/autopilot values through GIMOnline commands and data are passed through TelegramsThe Grex 2008 Azores MissionBecause GREX deals with multiple vehicles, a Go-To-Formation behaviour is necessary for each missionMy part in the mission:Developed an algorithm for Go-To-FormationHelped developing the software for telegram processing (communication on the vehicle side)Developed software to be ready to go to sea in Sesimbra, September 2008

Go-To-Formation: Spatially deconflicted path generation for simultaneous arrival in 2DGrex 2008 Azores Mission: ResultsPath Following

Picture is also showing the heading of the vehicle; given in local coordinatesGrex 2008 Azores Mission: ResultsTarget Tracking

Target Tracking experiment in azores. Catamaran following the guas Vivas. While the Catamaran was follwing the guas Vivas,in between for some time one of the thrusters of Catamaranwas failing, and the effect can easily be seen in the figure. The figure is plotted in local coordinates.

The Default Path is a remainder of other project settings; it is the path the vehicle should have followed if it hadnt received any data from guas Vivas.Future WorkIncorporate deconfliction in timeGo on to three-dimensional pathsFinally, think about on-line path planning during mission runtimePerhaps mention Prof Fatima Leite?

Thank you for your