On-board Fault Diagnosis and Fault Tolerant Control - IMS

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FRANCE - GERMANY - ITALY - THE NETHERLANDS - SPAIN - SWEDEN - UNITED KINGDOM 

Flight Mechanics, Systems and Integration Action Group FM (AG-16): 

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Laboratoire d’Automatique Productique 

Signal et Image 

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University of Bordeaux I - France 

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On-board Fault Diagnosis and Fault Tolerant Control 

GARTEUR Action Group FM(AG-16) Mid-Term Workshop, 4-5 April 2006, Airbus, Toulouse 

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FTC problem setting / constraints 

Basics of the design method 

A numerical example 

Some preliminary results (AG16 

benchmark) 


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– How to ensure an acceptable dynamical behaviour of 

the controlled system when faults occur. 

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– Deal with unanticipated/anticipated faults as quick 

as possible. 

– On-board detection, identification and diagnosis of 

performances degradations of system/subsystem 

critical faults for in-flight safe mission 

– Not to degrade the nominal performance in faultfree 

situations. 

– Ensure acceptable performance for the failed system 


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Occurrence of 

a fault 

The fault is 

detected 

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Behaviour with nominal control law 

Expected behaviour with FTC strategy 

integrated 


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– The nominal control law can not be modified / 

removed. 

– Undesirable bumps caused by activation of the FTC 

strategy should be adequately managed. 

– The transient behaviour during the time delay 

detection interval should be adequately managed 

(open question) 

– The diagnostic module (Hu and Hy) should be 

updated after a fault 


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– The design method uses only already available 

measurements which require only input-output 

processing for implementation in on-board 

computers. 

– Testability and certificability of the software 

implementation. 


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Switching logic 

may cause some undesired 

phenomena such as bumps or 

actuator saturation. 


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The overall strategy is illustrated using the 

well-known example +L0$7. 

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The control objective : a vertical 

translation. 

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The faulty scenario : an abnormal gain 

variation of 20% in the elevons actuators 

H 


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Mesured outputs to 20% of elevon flap failure 

Angle of attack (deg) 

10 

5 

0 

-5 

without FTC 

nominal FTC 

FTC+bump 

10 20 30 40 50 60 70 80 90 100 

Pitch angle (deg) 

15 

10 

5 

0 

-5 

without FTC 

nominal FTC 

FTC+bump 

10 20 30 40 50 60 70 80 90 100 

Time (s) 


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Elevon (deg) 

2 

1 

0 

-1 

Control of HiMAT vehicle 

without FTC 

nominal FTC 

FTC+bump 

-2 

10 20 30 40 50 60 70 80 90 100 

Canard (deg) 

4 

2 

0 

-2 

without FTC 

nominal FTC 

FTC+bump 

-4 

10 20 30 40 50 60 70 80 90 100 

Time (s) 


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● Linear model of the aircraft block : 


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● Linear model of the aircraft block (test scenario N°0) : 

● 

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– Turbulence and wind models are suppressed; 

– Fault models and the “)URP” flags (which are related to a “*RWR” 

flags of fault situation) are also suppressed; 

– Engines model is not taken into account; 

– The load factor Q ] is fixed to 1 (tips used in the old benchmark 

FTLAB747). 

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load factor specification 

for bank trim 

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● Linear model of the aircraft block (test scenario N°0) : 

● 

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– 6 states for longitudinal motion model: 

• {T, 9 7$6 , , , K H , [ H }. 

– 6 states for lateral motion model: 

• {S, U, , , , \ H }. 

– So, the states for total motion model: 

• {S, T, U, 9 7$6 , , , , , , K H , [ H , \ H }. 

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The differential equations do not depend of the states [ H and \ H . 

The order of linear model can be reduced. 

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Now, you can see that the differential equations do not depend of the states . 

Hence, the order of linear model can be reduced. 

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– So, we suppress three integral actions which correspond to the 

state variables [ H , \ H and . 

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● Validation of the computed linear model : 

– A step of magnitude 1ºis applied on the 4 elevators at the time 

W=50V. The non linear behavior is represented in blue and linear 

behavior in red. 

VTAS 

alpha 

theta 

delta e 

qbody 

2.02 

2.01 

2 

x 5010 100 150 

0 

-5 

-10 

50 

133.85 

100 150 

133.8 

133.75 

50 100 150 

0.0691 

0.069 

0.0689 

50 100 150 

0.0695 

0.069 

50 100 150 

he 

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pbody 

rbody 

beta 

phi 

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1 

0 

-1 

50 

1 

100 150 

0 

-1 

50 

1 

100 150 

0 

-1 

50 

1 

100 150 

0 

-1 

50 

1000.2 

100 150 

1000 

999.8 

999.6 

50 100 150 

Axb [m/s2] 

Azb [m/s2] 

0.677 

0.6765 

Specific forces in body axes 

0.676 

45 50 55 60 65 70 75 80 85 90 95 100 

Ayb [m/s2] 

1 

0 

-1 

45 50 55 60 65 70 75 80 85 90 95 100 

-9.775 

-9.78 

-9.785 

45 50 55 60 65 70 75 80 85 90 95 100 


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● Validation of the computed linear model : 

– A step of magnitude 1ºis applied to the THS at the time W=50V. 

The non linear behavior is represented in blue and linear behavior 

in red. 

theta alpha VTAS 

delta THS 

-1.24 

-1.26 

x 5010 -5 

100 150 

0 

qbody 

-10 

-20 

50 100 150 

133.85 

133.8 

133.75 

50 100 150 

0.0691 

0.069 

0.0689 

50 100 150 

0.0695 

0.069 

50 100 150 

/RQJLWXGLQDOPRWLRQPRGHO 

he 

phi 

beta rbody pbody 

/DWHUDO PRWLRQPRGHO 

1 

0 

-1 

50 100 150 

1 

0 

-1 

50 100 150 

1 

0 

-1 

50 100 150 

1 

0 

-1 

50 100 150 

1000.2 

1000 

999.8 

999.6 

50 100 150 

Axb [m/s2] 

Azb [m/s2] 

0.677 

0.676 

0.675 

Ayb [m/s2] 

1 

0 

Specific forces in body axes 

45 50 55 60 65 70 75 80 85 90 95 100 

-1 

45 50 55 60 65 70 75 80 85 90 95 100 

-9.77 

-9.775 

-9.78 

-9.785 

45 50 55 60 65 70 75 80 85 90 95 100 


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● 

● 

● 

● 

At this time (march 28, 2006), we are working on this 

linear model 

We are trying to run our FTC strategy within the 

benchmark environment. A precise functional analysis of 

B747 controller is needed … 

The goal is to run the FTC strategy first with FDI 

information available on-board, and second with 

integrated analytical FDI unit. 

Some changes should be included to deal with "stuck 

actuator' faults. 


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On-board Fault Diagnosis and Fault Tolerant Control - IMS

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