Transactions of Nanjing University of Aeronautics & Astronautics
Hybrid Fault Diagnosis and Isolation for Component and Sensor of APU in a Distributed Control System
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Abstract:
This paper addresses the gas path component and sensor fault diagnosis and isolation （FDI） for the auxiliary power unit （APU）. A nonlinear dynamic model and a distributed state estimator are combined for the distributed control system. The distributed extended Kalman filter （DEKF） is served as a state estimator， which is utilized to estimate the gas path components’ flow capacity. The DEKF includes one main filter and five sub-filter groups related to five sensors of APU and each sub-filter yields local state flow capacity. The main filter collects and fuses the local state information， and then the state estimations are feedback to the sub-filters. The packet loss model is introduced in the DEKF algorithm in the APU distributed control architecture. FDI strategy with a performance index named weight sum of squared residuals （WSSR） is designed and used to identify the APU sensor fault by removing one sub-filter each time. The very sensor fault occurs as its performance index WSSR is different from the remaining sub-filter combinations. And the estimated value of the soft redundancy replaces the fault sensor measurement to isolate the fault measurement. It is worth noting that the proposed approach serves for not only the sensor failure but also the hybrid fault issue of APU gas path components and sensors. The simulation and comparison are systematically carried out by using the APU test data， and the superiority of the proposed methodology is verified.
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V233.7
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