Examining Modal Vibration Analysis in Automotive Headlight Testing Systems

Automotive headlamps are critical for safety, but prone to vibration-induced misalignment, reducing visibility by up to 40–50% and risking non-compliance with UN/ECE and FMVSS standards. This study conducts modal analysis on a vibration test bench with a cam-based vertical stroke mechanism for headlamp durability, comparing fixed UCP 205 bearings with natural frequencies of 354.57–2831.6 Hz and rotational freedom mounts with 87.67–3347.4 Hz using SolidWorks Simulation. The first 10 eigenfrequencies, mode shapes, and effective/cumulative effective mass participation factors (EMPF/CEMPF) are evaluated to quantify directional dynamic dominance and to assess resonance susceptibility. Although the nominal operating range is 10–100 Hz, the rotational configuration introduces a resonance risk at 87.67 Hz (Mode 1), producing a maximum shaft deformation of 0.12 mm and implying potential bearing wear and headlamp misalignment under sustained excitation. In contrast, the fixed-bearing configuration shifts the lowest modes well above the operating band, indicating a stiffer support representation but potentially less realistic boundary compliance. Experimental validation at 35 Hz with 3.5 mm amplitude—selected to represent low-frequency road-induced vibration profiles—showed stable electrical and optical behavior with ±0.2 A current fluctuations. Noise measurements indicated levels exceeding 85 dB at 36 Hz, attributed to motor–cam interactions, representing an occupational exposure concern under TS EN ISO 9612 rather than structural failure. Based on the combined numerical and experimental findings, viscoelastic damping and improved isolation/noise mitigation are recommended to reduce resonance sensitivity and enhance test repeatability and accuracy.