Automotive Seat Vibration Testing with VM-S-100
1. Executive Summary
An automotive seat manufacturer needed to identify the resonant frequency and corresponding displacement amplitude of a seat headrest bracket to validate its structural integrity and ensure compliance with NVH (Noise, Vibration, and Harshness) standards. Using the non-contact Dynatronic VibroMicro VM-S-100 Laser Doppler Vibrometer, the company successfully characterized the bracket's dynamic response to swept-sine excitation, pinpointing its fundamental natural frequency with high precision.
2. Challenge
Component resonance in automotive interiors can lead to audible noise, perceived vibrations, and potential long-term fatigue failures. Identifying the fundamental natural frequency of components like seat headrest brackets is crucial for designing out these issues. Traditional contact sensors can add mass and alter the dynamic response of lightweight structures, potentially leading to inaccurate measurements.
3. Solution: Non-Contact Vibration Measurement
The Dynatronic VibroMicro VM-S-100 was deployed to provide a high-fidelity, non-contact measurement solution. Its key advantages for this application included:
Mass-Less Measurement: Eliminating the influence of sensor mass on the lightweight bracket, ensuring the measured response was authentic.
High Resolution: Providing precise displacement measurement, critical for quantifying vibration amplitude at resonance.
Rapid Setup: Allowing for quick targeting of the measurement point on the complex geometry of the bracket.
4. Test Setup
Device Under Test (DUT): Automotive Seat Headrest Bracket
Excitation: The DUT was mounted on a Shaker providing a Swept-Sine Excitation across a specified frequency range.
Measurement Equipment:
VibroMicro VM-S-100 Laser Doppler Vibrometer: The laser beam was focused directly on the headrest bracket at the critical test point.
Data Acquisition & Analysis:
Data Acquisition and Analysis Software (typically bundled with the VibroMicro system).
Matlab for advanced data post-processing and time-frequency analysis.
5. Data Analysis & Results
The vibration velocity/displacement data captured by the VM-S-100 was processed to generate a frequency spectrum.
Key Result:
Through comprehensive frequency-domain and time-frequency analysis, the fundamental natural frequency of the seat headrest bracket was clearly identified.
Natural Frequency: 12.8 Hz
Displacement Amplitude at Resonance: 1.037 mm
The results clearly show a sharp peak in the Frequency Response Function (FRF) at 12.8 Hz, confirming resonance with a significant displacement amplitude of over 1 mm.
6. Conclusion
The Dynatronic VibroMicro VM-S-100 Laser Doppler Vibrometer provided the automotive seat manufacturer with a fast and highly accurate method for dynamic characterization. The test successfully identified the resonant frequency and amplitude of the headrest bracket, providing critical data to guide design improvements and ensure the component does not resonate within the vehicle's typical operating frequency range, thereby enhancing overall cabin comfort and component durability. This case demonstrates the value of non-contact laser vibrometry in solving core NVH challenges in the automotive industry.
