Vehicle Gearbox Noise and Vibration
Contents
Series Preface
Preface
Acknowledgements
1 Introduction
1.1 Description of the TATRA Truck Powertrain System
1.2 Test Stands
References
2 Tools for Gearbox Noise and Vibration Frequency Analysis
2.1 Theory of Digitisation of Analogue Signals
2.1.1 Types of Signals
2.1.2 Normal Distribution
2.1.3 Mean Value and Standard Deviation (RMS) of a General Signal
2.1.4 Covariance
2.1.5 Mean Value and Standard Deviation (RMS) of a Sinusoidal Signal
2.1.6 Digitalisation of Signals
2.1.7 Signal-to-Noise Ratio
2.1.8 Sampling as a Mapping
2.2 Nyquist-Shannon Sampling Theorem
2.2.1 Antialiasing Filter
2.2.2 Sound and Vibration Measuring Chain
2.3 Signal Analysis Based on Fourier Transform
2.3.1 Time and Frequency Domain
2.3.2 Fourier Series for Periodic Functions
2.3.3 Fourier Transform of the Continuous-Time Functions
2.3.4 Short-Time Fourier Transform
2.3.5 Fourier Transform of the Discrete-Time Functions
2.3.6 Inverse Fourier Transform of the Discrete-Time Functions
2.3.7 DFT of a Constant and a Cosine Signal
2.3.8 Phasors as a Tool for Modelling Harmonic Signals
2.3.9 Example of DFT Calculation
2.3.10 Time and Frequency Scales
2.3.11 Spectral Unit of Autospectrum
2.3.12 Cross-Spectrum
2.3.13 Calculation of the Inverse Discrete Fourier Transform
2.3.14 Fast Fourier Transform
2.3.15 Time Window
2.3.16 Calculation of the Signal Power
2.3.17 Frequency Weighting
2.3.18 Analysis of Random Signals with the Use of Averaging in the Frequency Domain
2.4 Zoom FFT
2.4.1 Real-Time Zoom
2.4.2 Non-Destructive Zoom
2.5 Filtration in the Frequency Domain
2.5.1 Filtering
2.5.2 Integration and Calculation of Derivatives
2.6 Average Power of the Signal
References
3 Gearbox Frequency Spectrum
3.1 Source of Gearbox Noise and Vibration
3.2 Spectrum Signature
3.3 Low Harmonics of the Shaft Speed
3.4 Harmonics of the Fundamental Toothmeshing Frequency and their Sidebands
3.5 Subharmonic Components
3.5.1 Hunting Tooth Frequency
3.5.2 Effect of the Oil Film Instability in Journal Bearings
3.6 Ghost (or Strange) Components
3.7 Gear Rattle
3.8 Periodicity in Signals Measured on a Planetary Gearbox
3.9 Spectrum Components Originating from Faults in Rolling Element Bearings
3.9.1 Calculations for Bearing Defect Frequencies
3.9.2 Envelope Frequency Analysis
References
4 Harmonics and Sidebands
4.1 Harmonics
4.2 Sidebands
4.2.1 Amplitude Modulation
4.2.2 Phase Modulation
4.2.3 Mixed Modulation
4.3 Analytic Signal
4.3.1 Definition of Hilbert Transform
4.3.2 Calculation of Hilbert Transform of Sampled Signals
4.3.3 Demodulation of the Modulated Harmonic Signal
4.3.4 Unwrapping Phase
4.3.5 Normalising Phase
4.3.6 An Alternative Computing the Instantaneous Frequency
4.3.7 Envelope Analysis
4.4 Cepstrum
4.4.1 Effect of Harmonics
4.4.2 Effect of Sideband Components
4.4.3 Advantages of Cepstrum
References
5 Order Analysis
5.1 Speed Rotation Measurements
5.2 Order Analysis Based on External Sampling Frequency
5.3 Digital Order Tracking
5.3.1 Uniformity of Rotation
5.4 Frequency Domain Analysis Methods (Multispectral, Slice Analysis)
5.5 The Use of Order Spectra for Machine Diagnostics
5.6 Averaging in the Time Domain
5.6.1 Principle of Averaging in the Time Domain
5.6.2 Synchronised Averaging as a Comb Filter
5.7 Time Domain as a Tool for Gear Mesh Analysis
5.7.1 Averaging of Resampled Signals
5.7.2 Effect of Load on the Averaged Acceleration Signal
5.7.3 Average Toothmesh
5.7.4 Angular Vibrations
5.7.5 Effect of Averaging
5.7.6 Accuracy of the Incremental Rotary Encoders
5.7.7 Comparison of Averaging in the Time and Frequency Domain
References
6 Tracking Filters
6.1 Interpolation of the Instantaneous Rotational Speed
6.2 Quadrature Mixing as a Method for Amplitude and Phase Demodulation
6.3 Kalman Filter
6.3.1 Examples of the Use of the Kalman Filter
6.4 Vold-Kalman Order Tracking Filtration
6.4.1 Data Equations of the VK-Filter
6.4.2 Structural Equations of the VK-Filter First Generation
6.4.3 Structural Equations of the Second Generation of the VK-Filter
6.4.4 Global Solution of the Single Order Tracking Filtration
6.4.5 The Transfer Function of the VK Filter
6.4.6 Bandwidth of the VK Filter
6.4.7 The Frequency Response of the VK Filter
6.4.8 Global Solution for the Multiorder Tracking Filtration
6.4.9 Analytical Solution for Decoupling of Two Components
6.4.10 Iterative Methods of Solution
6.4.11 PCG Iterative Method
6.4.12 Initial Guess for the Iterative Solution
6.4.13 Comparison of the VK Filter of the First and Second Generation
References
7 Reducing Noise of Automobile Transmissions
7.1 Normal Probability Plot
7.2 Transmission Error Measurements
7.2.1 Averaged Transmission Error for a Circular Pitch Rotation
7.2.2 Transmission Error Measurements during Many Revolutions of Gears
7.3 Case Study
7.3.1 Historical Notes
7.3.2 Vehicle Pass-by Noise Measurements
7.3.3 Estimation of the Doppler Frequency Shift
7.3.4 Pass-by Noise Analysis with the Use of the Vold-Kalman Filter
7.3.5 Factory Limit for the Gearbox SPL
7.4 Gearbox Improvement Aimed at Noise Reduction
7.4.1 Gearbox Housing Stiffness
7.4.2 Geometric Design of Gears
7.5 Effect of Gear Quality on the Gearbox SPL
7.6 Effect of Operation Conditions on the Gearbox Vibrations
7.7 Quality Control in Manufacturing
References
Index