Integrated model-based and grey-relational-analyzed diagnosis of wheel speed sensor for aircraft antilock braking

The wheel speed sensor fault diagnosis for aircraft antilock braking system (ABS) is a difficult problem due to its poor working conditions and strongly nonlinear. To overcome this difficulty, a novel integrated model-based and grey-relational-analyzed diagnosis strategy is proposed. Due to its strong robustness, a sliding mode observer based on the aircraft braking model is employed to generate the residuals of the wheel speed. And grey-relational-analyzed diagnosis, which is known as its diagnostic accuracy and few computing requirement, is used for sensor failure diagnosis. Four different sensor states, namely normal state, gain variation failure, stuck failure, constant deviation failure, are simulated on an aircraft braking model and compared. The results presented indicate that this diagnosis strategy is capable of handing difficult wheel speed sensor failure.