Simulation of Gear Rattle to Aid in the Development of Sound Quality Metrics for Diesel Engine Component Specification

Transcription

1 Purdue University Purdue e-pubs Publications of the Ray W. Herrick Laboratories School of Mechanical Engineering Simulation of Gear to Aid in the Development of Sound Quality Metrics for Diesel Engine Component Specification Brandon Sobecki Purdue University Patricia Davies Purdue University J Stuart Bolton Purdue University, bolton@purdue.edu Follow this and additional works at: Sobecki, Brandon; Davies, Patricia; and Bolton, J Stuart, "Simulation of Gear to Aid in the Development of Sound Quality Metrics for Diesel Engine Component Specification" (2014). Publications of the Ray W. Herrick Laboratories. Paper This document has been made available through Purdue e-pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for additional information.

2 Simulation of gear rattle to aid in the development of sound quality metrics for diesel engine component specification Brandon Sobecki J. Stuart Bolton & Patricia Davies Ray W. Herrick Laboratory, Purdue University November 20, 2014

3 Research Sound quality is an important factor in the design of competitive engines Gear rattle is a phenomenon that can greatly affect the quality of the overall diesel engine sound Currently used metrics (such as A- weighed Sound Pressure Level) might not adequately address the role of gear rattle noise on the overall sound quality of the engine An understanding of human s response to the gear rattle noise is needed Simulations are needed for use in psychoacoustic tests designed to investigate detectable levels of gear rattle noise 2

4 Research Sound quality is an important factor in the design of competitive engines Gear rattle is a phenomenon that can greatly affect the quality of the overall diesel engine sound Currently used metrics (such as A- weighed Sound Pressure Level) might not adequately address the role of gear rattle noise on the overall sound quality of the engine An understanding of human s response to the gear rattle noise is needed Simulations are needed for use in psychoacoustic tests designed to investigate detectable levels of gear rattle noise 3

5 Research Outline Introduction s and objectives Gear Noise/Simulation Setting Setting Simulation /Future Work 4

6 Gear Mechanism (a) No Input (driving) gear (b) Output (driven) gear Stable (No ) if: Drag torque on output gear T d4 I Ý 4 4 (t) Inertial torque on input gear Taken from Singh, 1989 (Fig. 3) Unstable () if: T d4 I Ý 4 4 (t) * Cylinder firing events cause the inertial torque to exceed the drag torque (causing an impact) 5

7 Simulation Can we simulate sounds with gear rattle? Model rattle as impulsive events - Timing is keyed to combustion events A 1 (t t 1 ) A 2 (t t 2 ) K Time of combustion events Filter (gear cover) component 6

8 Simulation Simulation model developed using the difference between measurements with high and low amounts of gear rattle as a guide - The scissor gear data was used as the baseline (low gear rattle) measurement - The backlash measurement was selected as the high gear rattle case Assumptions for simulation development: - noise is independent of other engine noise - Teeth impact events occur due to pulsations in torque caused by combustion events (2 impacts per firing event) 7

9 Gear Simulation Model Set Set 8

10 Research Outline Introduction s and objectives Gear Noise Setting Setting Simulation /Future Work 9

11 Synchronizing to Baseline Measurement Instantaneous frequency tracks deterministic variation of speed of the engine and is used to synchronize of the gear rattle pulse train with the operation of engine - Baseline (Scissor Gear) signal was band-pass filtered around the firing frequency of the operating speed - Instantaneous frequency is calculated using the Hilbert Transform A sine wave with the instantaneous frequency characteristics as the baseline engine is generated to to guide in primary impact placement 10

12 Synchronizing to Baseline Measurement 11

13 Impact Placement The placement of the first impact is determined by T 1 (n) T sync (n) R 1 (n)[t sync (n 1) T sync (n)] Location of baseline synchronized guide value (firing event) Value chosen from uniformly distributed random sequence Period between current and subsequent firing events 12

14 Impact Placement The placement of the second impact is determined by T 2 (n) T 1 (n) (P SI R 2 (n))[t sync (n 1) T sync (n)] Delay from first impact (fraction of the current period between firings) Amplitude assigned to impacts is based on random sequence with uniform distribution Impacts are then turned off (chosen based on random sequence) 13

15 Research Outline Introduction s and objectives Gear Noise Setting Setting Simulation /Future Work 14

16 Gear Filter Goals of the filter design: - Estimate the spectral characteristics of rattle events - Filter pulse train to sound like gear rattle impact events Filter was designed as follows: Assume diesel and rattle noise are independent, so Baseline amplification factor S xr x R ( f ) S xhr x HR ( f ) G S xd x D ( f ) PSD of rattle noise signal PSD of signal with high rattle [Acadia.010 Backlash] Solve for the PSD of the rattle noise Design a digital minimum-phase filter, so that S xr x R ( f ) S xpt x PT ( f ) H rattle filter ( f ) 2 PSD of generated pulse train PSD of signal with little rattle noise [Acadia Baseline Scissor Gear] H rattle filter ( f ) S xr x R ( f ) S xpt x PT ( f ) 15

17 Gear Filter Decreased Damping The gear rattle impact events were judged to sound too Prony dull series or wooden model Original Impulse Response Prony Series Model In order to produce a metallic-sounding impact event, the damping of certain components of the impulse response of the filter was decreased A tap-test was performed at Cummins to identify resonant characteristics of the loaded gears and front cover A Prony series analysis was used to model the impulse response - Damping was reduced in selected terms with frequencies close to those of the gears and cover Decreased damping of Filter Impulse Response Original Impulse Response Decreased Damping (IR) 16

18 Research Outline Introduction s and objectives Gear Noise Setting Setting Simulation /Future Work 17

19 Gear Simulation - Baseline (Very Low ) High Measurement High Simulation 18

20 Gear Simulation - Baseline (Very Low ) High Measurement High Simulation 19

21 Gear Simulation - Signal SPL [db(a)] Loudness [N 5 ] [sone] Roughness [R 5 ] [asper] Sharpness [S 5 ] [acum] Tonality [K 5 ] [TU] Baseline Backlash Backlash Simulation

22 Research Outline Introduction s and objectives Gear Noise Setting Setting Simulation /Future Work 21

23 A simulation method has been developed to generate realistic sounding time histories with varying levels of gear rattle noise The independent control of the gear rattle noise with respect to the baseline engine noise was a useful tool in determining thresholds of detection and perception of growth of gear rattle The understanding gained from the development of this simulation method may help in the development of a gear rattle sound quality metric 22

24 References J.S. Bendat and A.G. Piersol. Random Data: Analysis and Measurement Procedures. Wiley, New York, 4 th edition, H. Fastl and E. Zwicker. Psychoacoustics: Facts and Models. Springer, Berlin, New York, A. L. Hastings. Sound Quality of Diesel Engines. PhD thesis, Purdue University, West Lafayette, Indiana, USA, August M.H. Hayes. Statistical Digital Signal Processing and Modeling. John Wiley and Sons, L. D. Mitchell. Gear noise: The purchaser s and the manufacturer s views. In Proceedings of the Purdue Noise Control Conference, pages , West Lafayette, Indiana, USA, A.V. Oppenheim and R.W. Schafer. Digital Signal Processing. Prentice-Hall, Englewood Cliffs, New Jersey, K. Shin and J. Hammond. Fundamentals of Signal Processing for Sound and Vibration Engineers. John Wiley and Sons, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ England, R. Singh, H. Xie, and R. Comparin. Analysis of automotive neutral gear rattle. Journal of Sound and Vibration, 131: , February R. Singh. Gear noise: anatomy, prediction and solutions. In Proceedings of the 2009 InterNoise Conference, Ottawa, Canada, August S. Singh. Prony analysis. March