6 Noise Dynamometers Must reproduce noise from vehicle testing Full-suspension capability (front/rear axle)Other key features:Climate controlLACT & matrix-type schedulesStandard objective assessment methodsLow background noise required for accurate assessmentRoller on some machines
7 NVH Problem Solving - Example 1.8 kHz noise problemModal analysis shows component frequencies not related to noise frequencyLaser vibrometer, noise dyno & vehicle used to provide solutionLaser identifies high vibration levels on leading edge inner padSolution - move inner pad clip by 1.5 mmSubjective/objective results:mm/s Mod605040302010
8 Creep-groan Creep-groan occurs at very low speeds, < 2rpm Used for core development material screeningVery low speed, high torque capability, allows relation of characteristics to vibration using full-size pads
9 DTV Generation and Cold Judder DTV generation subject to a wide range of factors (Driving style, Calliper characteristics, Friction material tribology & compressibility)Need to “screen” good/bad materialsKey to control of test lies in pad/disc contactIn a vehicle contact refreshed with periodic brake app’sDoes not guarantee reproducible results even on dynamometerControlled Contact Device maintains and controls pad/disc contact in ‘off brakes’ situationCompensates for wearDoes not require special caliper
10 High Speed (“Hot”) Judder Temp (C)700600500400300200Speed (Km/h)Frequency (Hz)DTV measurement systems and the F-M dual wavelength pyrometer may be used together to measure the effects of hot spotting
11 Advanced NVH Modelling Need to represent system componentsWe have good model-experiment correlation for system level modal analysesWe are continuing to develop our analytical modelling methods to give us a predictive capability
12 SummaryPerformance, refinement, time & cost are often conflicting compromisesStructured approach required for problem identification & solutionMore analytical work required
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