MACCCS UAV Semi-anual Review

Flight in Flow FieldsRicardo Bencatel

Department of Aerospace EngineeringUniversity of MichiganAnn Arbor, Michigan, USAApril 22nd, 2013R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields1Air Force RelevanceWhy?Persistent operationsFuel savingsLow noise signatureSmaller logistical footprint - Smaller UAVs

Can standard UAVs fly without fuel?R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields2

MotivationExtended UAVs endurance and rangeStandard UAV = Sensor & energy collectorHarvest air flow energy

*Edwards, D., Implementation Details and Flight Test Results of an Autonomous Soaring Controller, 2008R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow FieldsWith that in mind, we intend to extend the UAVs endurance, using unmodified UAVs and their airframes as sensors and energy collectors.How? By harvesting energy from the air flow where the UAVs are already flying.Furthermore, the exploitation of a phenomenon by groups of UAVs may be optimized if they share air flow information over their communication networks.This plot, by Edwards, illustrates a flight of about 70 miles, performed by an unpowered glider UAV, taking advantage of thermal updrafts.This proves UASs may benefit a lot from air flow energy harvesting.3Flight in Flow Fields

How can standard UAVs fly without fuel?R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow FieldsHere we have the aircraft kinematic equations, with the wind vector included, and the derivatives.If we combine that with the force equations4ApplicationApplications:Dynamic soaringHigh-altitude: Jet StreamLow/medium altitude: mountain ridgesLow altitude: oceans, lakes, flat landscapesGenerally: GustsStatic soaringPlains (including desert and ice/snow)Mountain ridgesPreliminary resultsSmaller UAVs benefit the mostExisting fleet endurance/range extension

R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields5Research FocusValidationModelsEstimationExploration MethodsExploitationMethodsEndurance ExtensionObservabilityR. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow FieldsLet me now present our research roadmap. ->We first started be studying the aircraft and flow field models and their interaction. ->During that study we understood that most models for the flow field phenomena that interest us were not validated against real data.As such, we develop a system to collect the necessary data for this validation. ->As our goal is to harvest energy from the flow field, we are studying the exploitation methods, in particular their dynamics and the feasibility limits. ->Now, to be able to use the flow field phenomena we need to know them, know their state.We considered that the measurements that allow us to estimate the flow field state are collected by the UAV itself, along its flight.As such, we studied the observability conditions for several flow field phenomena parameters.This allowed us to understand how the aircraft motion affects the flow field estimation process. ->The next step is to use this knowledge to design exploration methods, designing control strategies to optimize the phenomena observation and defining the estimation performance limits for each strategy. ->The last block required before the final implementation of energy harvesting system is the estimation.We developed different estimators for several of the flow field phenomena.Now the challenge is to validate them with real data and combine them, to get a comprehensive flow field estimate. ->Finally, we need to combine the exploration and exploitation strategies, and feed them with the flow field estimates to obtain an functional system, and then validate it.6Conditions for perpetual flight (Ph.D. dissertation)New models (Accepted for publication in the Journal of Progress in Aerospace Sciences)2 3D thermal models3 wind shear modelsFormation flight controller with collision avoidance (Presented at the CDC 2011)Observability and estimators (Ph.D. dissertation)Thermals (Presented at the AIS 2010)Wind Shear (Presented at the GNC 2011)

Current ContributionsR. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields7OutlineFlow Field PhenomenaFormation FlightDynamic Soaring

R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow FieldsDescribing motivation of this work.Introduce definition of a flow field and how it interacts with aircraft.Structure of this research effort.Quickly describe the flow field phenomena models we are studying.Introduce a formation flight controller.Describe current main focusFlight controller for dynamic soaring.8Flow Field PhenomenaValidationModelsEstimationExploration MethodsExploitationMethodsEndurance ExtensionObservabilityModelsR. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields9Wind currentsWind gradientsFlow Field PhenomenaBencatel, R., Sousa, J. B., and Girard, A. R., Atmospheric Flow Field Models Applicable for Aircraft Endurance Extension," Accepted for Publication in Progress in Aerospace Sciences, 2013.R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow FieldsThe atmospheric phenomena we are interested in are small time-space scale phenomena, unlike those widely studied by the atmospheric sciences community.We focused on three types of airflow phenomena that show most potential: thermals, wind shear and gusts.We selected those phenomena as their characteristics are well adjusted to the UAVs capabilities and dynamics.The study and development work we did on these models resulted in a survey article that was accepted for publication in the Journal of Progress in Aerospace Sciences.I will now go very quickly over the different models we studied, so we have enough time to address the other studies.10

ThermalsFlow Field Phenomena

R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow FieldsWind Shear

Flow Field Phenomena

R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields12

ValidationModelsEstimationExploration MethodsExploitationMethodsEndurance ExtensionObservabilityModel ValidationFormation FlightR. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields13Validate Thermals flow field modelSafely take spatially distributed samples

Formation Flight

April 22nd, 2013 14R. Bencatel (UM)Flight in Flow Fields14

Inter-UAV relative frame

Collision Avoidance strategy over the connecting axis:

Maximum velocity strategy over the orthogonal axis:Sliding Mode ControllerApril 22nd, 2013 15R. Bencatel (UM)Flight in Flow Fields15Kinematic Model

Controller (Feedback Linearization and Sliding Mode)

Information structureAll UAVs know each other and the leaderSliding Mode Controller

Ricardo Bencatel, Mariam Faied, Joo Sousa, and Anouck Girard, Formation Control with Collision Avoidance, 50th IEEE CDC and ECC, 2011April 22nd, 2013 16R. Bencatel (UM)Flight in Flow Fields16Formation Flight

R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow FieldsSimulation test- 5 UAVs starting very close to each other - Configuration completely different from the desired one- Converging to a cross shape formationGround reference frameInitial tests with real UAV:1 real and the rest simulatedOff-board controlPreparing final testsOn-board controlMultiple UAVsJournal paper17

Dynamic SoaringValidationModelsEstimationExploration MethodsExploitationMethodsEndurance ExtensionObservabilityExploitation MethodsR. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields18Dynamic Soaring

R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow FieldsTechnique to exploit the wind shearAlbatross:Sachs14000n.mi. in 48daysRC glidersUnpoweredWorld speed record 498mphThis technique may be used at:Ground level (like albatross do)Close the mountain ridgesWithin inversion layersJet-stream boundaries19Dynamic Soaring

R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields20Dynamic Soaring

R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields21Dynamic Soaring

R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields22Conclusions

R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields23ConclusionsValidationModelsEstimationExploration MethodsExploitationMethodsEndurance ExtensionObservabilityModels

Model ValidationExploitation MethodsFlow Field EstimationObservabilityFormation FlightThermalsWind ShearGustsDynamic SoaringWindThermalsR. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields24Ph.D. dissertation1 accepted journal paper4 accepted conference papers

PublicationsR. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields25AFRL:Dynamic SoaringPrecision air dropsUniversity of Porto & Portuguese Air Force

CollaborationsR. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields26Future Work

Can a flow field exploitation controller be introduced in a USAF UAV mission?How should the exploitation trajectories be combined?Can we harvest more energy if we have an electrical regeneration system?Are the presented thermal and wind shear models valid?Usefulness - How frequent are the studied?R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields27Future WorkValidationModelsEstimationExploration MethodsExploitationMethodsEndurance ExtensionObservability

Model ValidationExploitation MethodsFlow Field EstimationPrecision Air DropsExploration MethodsEndurance ExtensionFormation FlightDynamic SoaringWindGradientsVolumeLanding Point Approach ControlR. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields28

Flight in Flow FieldsRicardo Bencatelbencatel@umich.edu

Department of Aerospace EngineeringUniversity of MichiganAnn Arbor, Michigan, USAApril 22nd, 2013R. Bencatel (UM)April 22nd, 2013 nR. Bencatel (UM)Flight in Flow Fields29