Basics of NVH Frequency Analysis (Interactive Web Training)

For NVH measurements it is crucial to understand how and why changing FFT parameters results in different spectral representations. This is beneficial either when you follow standardized procedures for an FFT analysis or if you require troubleshooting for NVH phenomena.

This interactive web training will provide rules of thumb for signal analyses relevant to the measurement chain, especially for FFT analyses. The training objective is to deliver a basic understanding of concepts behind digital frequency analyses (FFT) and of reasonable parameter settings for basic measurement tasks like stationary or run-up measurements .

Topics

DUT (device under test) and excitation signal types | AD conversion with resulting digital throughput: rules of thumb concerning sampling rate and measurement range | Understanding the influence of FFT parameters based on a throughput data block with n samples | Analysis of throughput: FFT, order analysis | Basics of frequency and time domain filters in the PAK graphics.

Approach

Instead of a mainly mathematical approach, we will rather look at graphic illustrations of the relevant signal analysis concepts, typical level plot representations of measurement data, Campbell diagrams for frequency and order analysis

Program

Day 1:

• Phenomenological approach to signal analysis parameters: FFT analysis of vehicle run-ups in PAK
• Excitation phenomena and signal classes (periodic, transient, random), uncertainty relation
• How to get the throughput: Sampling of continuous signals and resulting properties for the discrete Fourier transform; Quantization of signals

Day 2:

• Practical consequences and rules of thumb for FFT analysis

• Phenomena in the frequency domain: Energy concept and frequency resolution, leakage and windowing, picket fence effect and amplitude accuracy, overall calculation

• Non-stationary measurements (overlap of FFT blocks)

• Campbell representation and tracking parameter rpm

Day 3:

• Order analysis: Orders obtained via FFT and via Digital Order Tracking (angle domain)

• Filtering in the frequency and time domain: This is an important field for processing NVH data. A short introduction for the usage of filters in PAK, based on three rules of thumb will be offered

Course language: ENGLISH