Reconfigurable Control Strategies: Towards Fault Tolerant and High Confidence SystemsGeorge VachtsevanosGeorgia Institute of TechnologyAtlanta GA 30332-0250
SWAN 06The University of Texas at ArlingtonDecember 7 9, 2006
Flight Results Bob Up
Collective Failure Scenario
The ProblemImproving UAV reliability is the single most immediate and long reaching need to ensure their success. - OSD UAV Roadmap 2002-2027Unmanned aerial vehicles require a fault-tolerant control (FTC) architecture that allows them to generate and track safe flight paths before and after the occurrence of a fault.
The Anatomy of a FailureHydraulic fluid swapped for engine oil during maintenanceMore volatile lubricant evaporates increasing frictionIGB output bearing overheatsBearing fails from excessive heat SH-60 loses tail-rotor authority SH-60 grounded for IGB servicingHydraulic Fluid Runs Red by LCdr. Patrick KennedyMech, Winter 2001
Aircraft Mishaps/Failure ModesRetired Marine Lt. Gen. Bernard Trainor said the issue of aging aircraft is a constant complaint of all branches of service.Atlanta Journal ConstitutionApril 27, 2002
Testing, Modeling, and Reasoning Architecture for Fault Diagnosis and Failure PrognosisTesting/Seeded Fault DataModelingReasoning Architecture for Diagnosis-PrognosisIntermediateGearbox (IGB)fitted with VMEP sensors to monitor components Prevent unscheduled maintenance Assist the pilot in making intelligent decisions about air-worthinessVMEP/HUMSmodules
The Fault Diagnosis/Prognosis Architecture
Space Engine Fault AccommodationBody Flap ControllersElevonControllersRudderControllersComponent Degradation andSystem Performance Model(From Task 2)Prognostic & DiagnosticAlgorithms(From Task 4)Run-TimeDemo SystemActuator CommandsActuatorPerformance DataSystem Requirements(Task 1)Model Validation(Task 3)Integrated Flight Control System Logic(From Task 5)
Helicopter Active System RestructuringRPM control CollectiveTail rotorSwashplate actuatorsS/P Actuator AdA S/P Actuator BdBS/P Actuator CdC Tail Rotor PitchdtrActive Control:Long. Cyclicdlon Lateral CyclicdlatCollective Pitchdcoll Tail Rotor Pitchdtr
Alternate means of restructuring employ: tandem rotors, stabilator control, individual blade control, jettisoning of storesLong. Cyclicdlon Lateral CyclicdlatCollective Pitchdcoll Tail Rotor Pitchdtr
Adapts the position, velocity, acceleration, and/or jerk for the assigned waypointsProvides a simple exportable model (HURT)Implies a change to the aircraft time of arrivalWith or without reconfigurable path planningMission Adaptation
Reconfigurable Flight ControlBaseline controllerInverted Model PDReference Model RPM sensor:Feedback Linearization:-+Plant
Adaptive Neural Network
Flight Results - Stuck Collective
Challenges for Control EngineersRobust, reliable and timely fault diagnosis and prognosisInterface requirements to system controllersSystem design to accommodate fault isolation, system restructuring and control reconfigurationControl reconfiguration technologiesHigh Confidence Systems!
Intelligent Fault Diagnosis and Prognosis for Engineering Systems
This is a summary of the demo plans for next summer.This presentation has focused on rotary-wing technologies, but many of the controllers and tools are being applied in a Boeing-led group to the F-15 and UCAV. The OCP is going to transition to UCAV as the mission management system in the next block (block 2). In the fixed-wing demo, we will control use the T-33 UCAV surrogate in formation flight, trajectory regulation, and weapons-release control scenarios.