FAULT DETECTION

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FAULT DETECTION IDENTIFICATION / RECONFIGURABLE
CONTROLOCP IMPLEMENTATION

• Scott Clements
• 20 March 2003
• School of Electrical and Computer Engineering
• Georgia Institute of Technology, Atlanta, GA 30332

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FTC Hierarchical Architecture
Fault Scenario Manager
Fault Detection Identification
HighLevel
MidLevel
Low Level GainController
RedistributionController
Set-PointController
Interconnection Structure
v1
LowLevel
Subsystem
Subsystem
y1
r1
e1
Local Controller
Local Controller
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Fault Detection vs.Controller Reconfiguration

• Two stages to FTC
• Fault Detection and Identification (FDI)
• Detects the presence of a fault
• Identifies the fault
• Controller Reconfiguration
• When alerted by the FDI routine, reconfigures the
  control by any or all of the following (where
  applicable)
• Changes interconnection topology between
  subsystems
• Adjusts subsystem set points
• Adjusts low level controller gains

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Potential Actuator Failure Scenarios
Scenario
Description
Effect
Reconfiguration
Main rotor collective is stuck in a known
position.
Vertical acceleration can not be controlled by
the collective.
Use RPM to control vertical acceleration.
1. Stuck Collective
Use altitude (or vertical acceleration) to
compensate for loss of rpm control (i.e.,
Autorotation).
Throttle is stuck in a known position or goes to
zero (engine failure).
RPM can not be governed as is traditionally done.
2. Throttle Stuck / Engine Failure
Use thrust and collective control to control yaw
acceleration.
3. Tail Rotor Stuck / Transmission Failure
Tail rotor is stuck at a given pitch or stops
rotating altogether.
Yaw acceleration can not be controlled by the
tail rotor.
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Implementation Architecture
FDI
stateIn
GtmaxState
GtmaxLink
GTMaxNavigation Control
stateOut
fdiOut
ethernet UDP
FaultDeclaration
RPMController
fdiIn
commandIn
stateIn
triggerIn
SW Trigger
Primary FlightComputer(onboard)
commandOut
GtmaxCommand
Secondary Flight Computer (onboard2)
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ComponentInfo.txtSignal Type Definitions
Signal GtmaxState Data char navStatus
char gpsStatus char sonarStatus
char radarStatus char magnetStatus
char overrun char wow char autopilot
char lavoid double time double
x double y double z double vx
double vy double vz double q1
double q2 double q3 double q4
double p
Signal faultDeclaration Data double
faultCondition
Signal GtmaxCommand Data int type
double x double y double z
double vx double vy double vz
double q1 double q2 double q3
double q4 double p double q
double r double delm1 double delm2
double delm3 double delf double
refrpm double fdideclaration double
stuckdelcmdr
double q double r double rpm
double altitudeAGL double tl_delcmdr double
ol_delcmdr double a_b_e_B2 double v_b_e_B0
double v_b_e_B2 double w_b_e_B0 double
w_b_e_B1 double w_b_e_B2 double traj_v0
double traj_v1 double traj_v2 double
traj_x2 double traj_psi double ax double
ay double az double delfhat

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ComponentInfo.txtComponent Type Definitions
Component GtmaxLink Input triggerIn
Trigger S/W Input commandIn Receives
GtmaxCommand Output stateOut Sends
GtmaxState Behavior TriggerAvailable
Inputs triggerIn Outputs stateOut
Behavior CommandAvailable Inputs commandIn
Component fdi Input stateIn Receives
GtmaxState Output fdiOut Sends
faultDeclaration Behavior StateAvailable
Inputs stateIn Outputs fdiOut
Component rpmController Input fdiIn
Receives faultDeclaration Input stateIn
Receives GtmaxState Output commandOut
Sends GtmaxCommand Behavior StateAvailable
Inputs fdiIn, stateIn Outputs
commandOut
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ComponentInfo.txtProcess Definitions
Process 1 Component GtmaxLink gtmaxLink
triggerIn, PERIODIC, HIGH_CRITICALITY, 0.001
commandIn, PERIODIC, HIGH_CRITICALITY,
0.001 stateOut, PERIODIC,
HIGH_CRITICALITY, 0.001 Component fdi FDI
stateIn, PERIODIC, HIGH_CRITICALITY, 0.001
fdiOut, PERIODIC, HIGH_CRITICALITY,
0.001 Component rpmController RPMController
fdiIn, PERIODIC, HIGH_CRITICALITY,
0.001 stateIn, PERIODIC,
HIGH_CRITICALITY, 0.001 commandOut,
PERIODIC, HIGH_CRITICALITY, 0.001 Connections
FDI.stateIn, gtmaxLink.stateOut
RPMController.fdiIn, FDI.fdiOut
RPMController.stateIn, gtmaxLink.stateOut
gtmaxLink.commandIn, RPMController.commandOut
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ComponentInfo.txtHybrid State Definitions
Hybrid_States Default_State Mode1 Mode1
gtmaxLink.triggerIn, HIGH_CRITICALITY,
(50) gtmaxLink.commandIn,
HIGH_CRITICALITY, (50) gtmaxLink.stateOut,
HIGH_CRITICALITY, (50) FDI.stateIn,
HIGH_CRITICALITY, (50) FDI.fdiOut,
HIGH_CRITICALITY, (50)
RPMController.fdiIn, HIGH_CRITICALITY, (50)
RPMController.stateIn, HIGH_CRITICALITY,
(50) RPMController.commandOut,
HIGH_CRITICALITY, (50)
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Integration with GTMax
On board
On board2
On board UAV
Secondary flight computer
Primary flight computer
ethernet
Wireless ethernet
Wireless serial
Hierarchical architecture with FDI and FTC on the
OCP
GCS
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FDI Algorithm for Stuck Collective

• NN is trained off-line using any available data
  (SITL, HITL, and/or flight test)
• Runs continuously
• May need faster rate/higher priority as a fault
  becomes evident

Pos (z)

FDI (Neural Network)
Fault Manager
From Sensors
Vel (z)
Fault Confidence
Acc (z)
Collective command

From LL Controller
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FDI Integration with GTMax
OCP on secondary computer
FDI (Neural Network)
Fault Manager
Fault Confidence
FaultInfo
FDIInfo
GTMaxLink
Process 1
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Nominal Configuration
Mode Transitioning
Fault Detection Identification
Fault Manager
Mission Planning
High Level
Limit Avoidance
Fault Tolerance
FTC (idle)
Trajectory Planning
EnvelopeProtection
Mid Level
Low Level
Low Level Controller
Throttle Command
Engine
Collective Command
Actuator
GTMax
Tail Rotor Command
GTMax
Sensors
Actuator
Lat. Cyclic Command
Actuator
Long. Cyclic Command
Actuator
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Fault Configuration (Stuck Collective)
Fault Detection Identification
Fault Manager
Mission Planning
High Level
FTC (active)
Trajectory Planning
EnvelopeProtection
Mid Level
Reconfiguration!
Low Level
Low Level Controller
Throttle Command
Engine
Collective Command
x
Actuator
GTMax
Tail Rotor Command
Aerodynamics
Sensors
Actuator
Lat. Cyclic Command
Actuator
Long. Cyclic Command
Actuator
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FTC Algorithm forStuck Collective

• In general, uses optimization routines to adjust
  the interconnections, set points, and low level
  controller gains (where applicable)
• In this scenario, the physical system only allows
  manipulation of the set points (actuator
  commands, including throttle)

Fault Manager
FaultInfo
FTC
LL ControllerOutput
Actuator Commands
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FTC Integration with GTMax

• When the Fault Manager declares a fault, it must
  start the FTC routine and reconfigure the its
  connections as shown previously.
• FTC routine should have a high priority.

OCP on secondary computer
Process 1
Fault Manager
FaultInfo
Process 2
FTC
LL ControllerOutput
Actuator Commands
GTMaxLink