NVH Challenges in Head Up Display (HUD) Design for Modern Connected Vehicles: Balancing Performance and Structural Dynamics

A more recent focus on driver comfort and the increasing demand for access to information make automotive OEMs provide advanced features such as Head Up Display systems. Even though HUD projects vital information onto the windshield/glass, its structural integration comes with significant noise and vibration challenges, leading to noisier in-cabin, display instability and haziness. This paper discusses the significant design parameters influencing the in-cabin NVH levels and functional effectiveness of HUD systems. The structure considered for analysis is the HUD assembly and its integration in vehicle. CCB turns out to be the critical component of the vehicle structure susceptible to road excitations although its mass dampens the vibrations inherently, due to the low mass of the HUD, relative oscillation between its projector, mirror, and either the windshield or display causes image distortion. In addition, the fan incorporated to cool the projector possess threat to in-cabin sound quality and steering wheel vibration due to its close proximity to the driver ear and tactile locations. This paper investigates in detail the role of HUD structural stiffness, eccentric design and material of the display glass and its shaft in achieving optimal HUD functional performance. The system natural frequency has to be above the dominant road excitation or the critical flickering frequency (CFF) to avoid resonance and fuzzy images. This paper also explains how fan rpm, its balancing and the motor excitations should be strategically designed so that in-cabin and tactile vibration can be kept within the limit. This data is used to build a robust CAE model with which future HUD designs can be developed and validated. The research may be of vital assistance to automotive engineers in designing robust functional HUD systems. Addressing the above critical design parameters, this paper paves the way for a seamless HUD experience in modern connected vehicles.