Diagnostics of actuation system by Hadamard product of integrated motor current residuals applied to electro-mechanical actuators

Sreedhar Babu G., Sekhar A.S., and Lingamurthy A
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Full Paper
ijphm_19_022.pdf4.19 MBNovember 1, 2019 - 2:23am

The paper presents the diagnostics methodology that can be used for flight actuation systems driven by Linear Electromechanical Actuators (LEMA). In case of LEMA driven flight actuation systems, the faults outside the actuators are difficult to be detected due to higher mechanical advantages of transmission elements like roller screws, gear train and linkage arms scaling down their effects before reaching the motor. One such event occurred, wherein the jet vanes of thrust vectoring system were sheared when back driven by excessive gas dynamic forces. Neither the motor current nor the LEMA position feedback data has any clue of the instance of occurrence. The side forces due to the deflection of the vanes actually measured were higher than predicted forces by Computational Fluid Dynamics (CFD) leading to failure. The case study is discussed in detail. A new diagnostic methodology to pin point the event of occurrence is arrived at using static test data. The same is reassured using lab experiments on three samples. The method's applicability is also extended for extracting events in actual flight, by comparing the flight telemetry data with the lab level data. The methodology uses LEMA motor current to arrive at the diagnostic information. The current data of LEMA directly can't be interpreted due to its pulsating form because of the pulse width modulation (PWM) switching, threshold voltages and closed loop dynamics of the servo. Hence, the motor current is integrated using cumulative trapezoidal method. This integrated data is used for curve fitting. The Hadamard product is used on the residuals of curve fitting to amplify the information and suppress the noise. Normalizing is done to compare across tests and samples. With this, the diagnostic information is ex tractable from static test data.The method is extended for extracting similar information from comparison of actual flight data and lab level dry runs. The method is also verified for both back driven and actuator driven failures.

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Submission Keywords: 
Flight control actuation systems
Electro mechanical actuators
Linear electro mechanical actuators
Submission Topic Areas: 
Data-driven methods for fault detection, diagnosis, and prognosis
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