27 Fault Diagnosis of Helicopter Gearboxes Kourosh Danai

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University of Massachusetts

27.1 Introduction ........................................................................ 27-1

27.2 Abnormality Scaling ........................................................... 27-5

27.3 The Structure-Based Connectionist Network .................. 27-8

27.4 Sensor Location Selection .................................................. 27-11

Coverage Index † Overlap Index † Monitoring

Effectiveness

27.5 A Case Study ....................................................................... 27-14

Structural and Featural Influences † Evaluation of Influences †

Fault Detection Results † Fault Diagnostic Results † Sensor

Location Evaluation † Sensor Location Validation

27.6 Conclusion .......................................................................... 27-23

Summary

An overview of fault detection and diagnosis of helicopter gearboxes is presented in this chapter. Between oil

analysis and vibration monitoring, the two predominant methods of gearbox monitoring, vibration monitoring

is much more studied and relied upon because of its ability to reflect a wider variety of faults. In order to

cover the concepts used in vibration monitoring, a method of diagnosis is discussed that relies on the

knowledge of the gearbox structure and characteristics of the features of vibration for component fault

isolation. Since a necessary part of vibration monitoring is selection of accelerometer locations on the housing,

a method is also described whereby the suitability of accelerometer locations is quantified based on the

structure of the gearbox and the monitoring effectiveness of the locations. Finally, a case study is included to

illustrate the application of the concepts presented in the chapter to fault detection and diagnosis, as well as

the ranking of suites of accelerometer locations. Some topics related to this chapter are covered in Chapter 15,

Chapter 25, and Chapter 26.

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