Automotive NVH Research Instrumentation and Infrastructure at UC-SDRL

Transcription

1 Automotive NVH Research Instrumentation and Infrastructure at UC-SDRL Teik C. Lim, Jay Kim, Randall Allemang Structural Dynamics Research Laboratory Mechanical, Industrial & Nuclear Engineering University of Cincinnati

2 Long-term Objectives Integrated experimental, analytical & computational research laboratories y Drivetrain and propulsion noise & vibrations y Vehicle system dynamics and control y NVH and acoustic noise quality Discovery, research and education-centered facility y Training of next generation engineers y Partnerships with industry and government y Conception & deployment of new technologies (new challenges: wider use of alternative fuels/systems)

3 Research Focus Study of forces/motions FEM/modal analysis Spectral techniques Noise path analysis Drivetrain Systems (Gears, Bearings, Trans., Engines) Nonlinear response/stability Active control / smart systems Noise/Vib Control Vehicle Structures (Body, Chassis, Interior Acoustics) Structure-borne contributions Hybrid models Vibro-acoustic design/analysis NVH & Sound Quality (Actuators, Brakes, Rotating Machines) Audio-visual simulations Jury Evaluation / statistical models Signal analysis Target setting

4 Major Research Infrastructure 4-axis nonlinear road simulator Advanced modal/spectral analysis Gear dynamics/acoustics Clutch Coupling Test Gearbox Torque & Speed Transducers Isolating Belt/Pulleys Test Foundation Drive Motor Slave Gearbox for Torque Application 1 in. Anechoic chamber Acoustic noise quality studio Computational Vibro-acoustics

5 4-Axis Road Simulator MTS Series 3 Data Acquisition Equipment: HP-36X Modules 4-ch (1. khz) & 4-ch ( khz) HP-VXI Modules 96-ch ( khz) Larsen Davis Network System 64-ch ( Hz) Application Areas: Squeak & Rattle Nonlinear Response Ride quality Software: MTS Ideas LMS Matlab Computers: HP-UX workstations Windows NT/

6 4-Axis Road Simulator (Results)

7 Inverse Sub-structuring (Spectral Domain) {x o(a) } {x c(a) } [K] {x c(b) } {x o(b) } Free sub-structure structure A {f c }=[D A ]{x c } {R c(a) } {R c(b) } Free sub-structure structure B {f c }=[D B ]{x c } {f i(a) } {f c(a) } Inversion {f c(b) } {f i(b) } {x c }=[H c ]{f c } Frequency-dependent Nonlinear Algebraic Solutions (express free sub-structure FRFs in term of system response) One-dimensional case H o(a)c(a) = K ( H H H ) = s,c(a)c(a) H ( H H ) s,c(b)c(b) s,c(a)c(a) s,c(b)c(b) H H s,c(a)c(b) s,c(b)c(b) s,c(a)c(b) H s,c(a)c(b) H s,c(a)c(b) H s,c(a)c(a) s,o(a)c(a)

8 Vehicle Structure (Chassis Force Transmissibility) Data Acquisition System Spindle excitation test Accelerometer Test vehicle Road Noise/Vib VXI frontend Air mount support Modal Hammer Impact hammer sub-structure A mic, o(a) Body structural-acoustic Sensitivity response Frame/suspension dynamics (Transmissibility and Resonance Effects) Chassis force input to body Spindle Loads Tire patch excitation c(b) c(a) i(b) accel o(a) sub-structure B mount

9 Vehicle Structure (Validation Results) Stiffness (kn/mm) 1 1 Rear left mount stiffness Measured (Elastomeric test) Predicted Frequency (Hz) Sound Pressure (db) Driver's ear SPL due to spindle force Predicted Measured Frequency (Hz) Method to dissect system response into free sub-structure characteristics Modular viewpoint to study dynamic response of complex structures Readily provides force transmissibility and path contribution functions

10 Crank Rumble (Nature of Problem) Transient, rough sound due to combustion-induced crankshaft vibration Most severe in 4-cylinder, manual transmission powertrains Correlation between the annoyance level and main journal clearance Ramp-up Ramp-down Neutral no-load snap test Rumble contains several modulated, constant, narrow-band signals Spectrogram Function (time-frequency analysis)

11 Periodicity of Rumble (Engine speed effect) Specific loudness & moving average filters SPL rumble period Modulation Frequency band: 87 9 Hz slope = p/6 p=. (half-order effect) Time scale Engine rpm Half-order effect implies sensitivity to a specific cyl. or main journal brg. Speed-invariant frequencies suggest effects of structural modes.

12 Rumble Transmission (Simulated Air-borne) Sound Quality Playback System Baffled Speaker DAT Recorder TL Input Signals No-load snap nd gear ramp Random noise Mic Specific Loudness Reduction Operating Data Simulated Data Bark Hz Air-borne dominance Simulated Data Same effect for Barks thru 7 (4-1, 1-63, Hz) Bark Hz Operating Data Structure-borne dominance

13 Damping Identification (Hybrid Modeling) Direct damping identification from measured dynamic stiffness matrix Imaginary([H(ω)] -1 ) = [C(ω)] Represent true loss mechanism & spatial distribution in freq. domain Use with analytical mass and stiffness matrices to form a hybrid model - x Real x 1 9 Imag - x x x x x 1 9 x x 1 9 x x 1 9 x 1 9 Typical results: Diagonal elements of experimentally identified damping matrix

14 Sound Transmission (Anechoic Facility) 4 Calculated Me a s ure d 3 TL (db) 1 Cylindrical structure Fre quency (Hz) 4 3 W/ S tiffe ne r W/O S tiffener Flat-stiffened 1 9 Cylindrical-stiffened W/O stiffener W/ s tiffe ne r TL (db) TL (db) Fre quency (Hz) Frequency (Hz)

15 Concluding Remarks New challenges requiring integrated test & analysis facility for research, education and services y Nonlinear & time-varying problems y More stringent NVH requirements y Combined design & NVH analysis/testing approach y Alternative vehicle, propulsion and fuel systems Center for discovery, research and education y Repository for basic and applied NVH technologies y Partnerships between academia, industry and govt. y Combined research & education activities