Positioning Criteria for Automotive Headlamp Module Supports Using Transmitted Force and Natural Frequency

Headlamps are one of the most important parts of vehicles because they contribute to the vision and safety of the driver. However, rough road conditions create harsh external excitations, which could loosen bolts in the headlamp assembly and cause improper aiming of headlight. Additionally, headlamps must be robustly designed because supporting positions of their assembly are typically determined based on the initial design of vehicle chassis without considering the occurrence of vibration fatigue. Therefore, under driving conditions, the headlamp assembly may experience excessive excitation forces, which loosen supporting bolts and arbitrarily change the aiming and adjustment of the headlight. To solve these issues, in this study, the authors propose positioning criteria for the headlamp bolts by predicting the transmitted force and natural frequency when external excitation forces are applied. First, the equations of motion for a conventional headlamp model are derived via lumped parameter modeling. Next, the transmitted force at each supporting point and natural frequency are calculated and utilized in the positioning criteria. Then, several cases are validated using experimental and computer aided engineering (CAE) results. Finally, positioning criteria for the headlamp bolts are suggested by combining the transmitted force and natural frequency.