## 5 Conclusions and Future Research Directions  
This study aimed to mitigate vibrations in vehicle sunroofs and ensure structural stability through design optimization. The actual vibration levels and characteristics of sunroof glass were investigated by calculating the equation of motion and natural frequencies using thin plate theory and validating these findings with experimental tests. An EMA test was conducted on a vehicle equipped with accelerometers to measure vibrations with an impulse hammer in the laboratory, while an ODS test was performed on the same object during vehicle operation (cruising condition with constant velocities). This facilitated an assessment of vibration phenomena within the vehicle sunroof system, focusing on parameters such as the natural and resonance frequencies. First, the inherent vibration characteristics of sunroof glass when installed on a vehicle were examined using EMA testing. The tests were conducted at varying sunroof positions, revealing clearer vibrations at increased opening levels. Subsequently, ODS testing was conducted to validate the findings under real driving conditions, considering road surface and speed factors. A comparative analysis between EMA and ODS results confirmed the resonance frequencies, showcasing minor deviations between the two methods. Based on the experimental vibration data, 3D modeling of the sunroof glass was used to analyze the changes according to the key design factors: [PERSON]'s modulus, glass thickness, and bracket position. * [PERSON]'s modulus variation: As [PERSON]'s modulus increased or decreased, resonant frequencies showed the corresponding changes, exhibiting a linear relationship. This indicates a potential avenue for improving the vibration characteristics without significant structural alterations. * Glass thickness alteration: Similar to the [PERSON]'s modulus, increasing the glass thickness leads to higher resonant frequencies and vice versa. On the other hand, the rate of frequency change decreased as the thickness decreased, raising considerations for manufacturing cost efficiency. * Bracket position adjustment: Changing the distance between brackets affects the resonance frequencies linearly, with larger changes resulting in larger frequency shifts. Increasing the bracket distance enhanced the dynamic rigidity, suggesting potential design improvements. The contributions of this research are as follows. Figure 22: Change in natural frequency due to a change in design factors of: (**a**) [PERSON]’s modulus, (**b**) glass thickness, (**c**) distance between brackets. 1. Experimental work for vibration measurements of the whole vehicle were conducted \"during operation\" with the sunproof system installed, while prior investigations were constrained to examining the static rigidity of a single part. 2. An effort was undertaken to establish reliability among different methodologies through a comparison of theoretical, analytical, ODS, and EMA results. 3. On this basis, parametric study-based optimization process is conducted, and it is confirmed that an optimal design is feasible to reduce the vibration of the vehicle sunproof that occurs while the vehicle is in motion. The novelty of this work can be found in the vibration measurements in driving conditions, which are validated with theoretical, analytical, and EMA results. Thus, this type of work can be employed in other applications by replicating this process. Although the amounts of change in the parameters were relatively minimal (limited to the range set, not the entire possible range), they show that there is some possibility for improving vibration through parameter changes. Future research should expand optimization methods, considering various sunproof types and vehicles. Also, there should be investigations with regards to the functionality of the sunproof affected by the parameter changes. Exploring additional design factors and cost optimization is also warranted.