# Bionic Design of the Vertical Bracket of Wide Angle Auroral Imager by Additive Manufacturing
## 6 Conclusions  
In this work, we have designed the vertical bracket for wide angle auroral imager by integrating structural bionics and structural optimization and then manufactured by SLM. We have applied, for the first time, the morphological characteristics of femur to the design of aerospace supporting structure. The upper structure is convex at both ends and concave in the middle. The upper and lower parts are wide and the middle is narrow. The middle width of the vertical support is determined on the basis of the width-to-diameter ratio. According to the bone mineral density distribution of femur, the middle position of the vertical support is designed as a solid structure, and the upper and lower ends are designed as hollow thin-plate structures to meet the requirement of lightweight and structural stiffness. Structural optimization is applied in two stages of vertical support bracket design. Topology optimization is used in the conceptual design stage to find the optimal structural distribution and obtain the preliminary model of the structure. After structural bionics design, size optimization is employed to obtain the optimal structural model. Further, the feasibility of the bionic optimized design is verified by simulation analysis and experiment. Compared with the simulation analysis of the original design and the structural bionic optimized design, the first three-way eigenfrequencies of bionic optimized structure are 320 Hz, 303 Hz, and 765 Hz, which are closely approximate to the  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Direction** & **x** & **y** & **z** \\ \hline Low-level vibration test results/Hz & 307 & 292 & 736 \\ Simulation results/Hz & 320 & 303 & 765 \\ Error rate & 4.2\% & 3.7\% & 3.9\% \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of small-scale characteristic sweep test results and simulation results.  
Figure 9: Vibration test on the vertical bracket. (**a**) Schematic diagram of vibration test. (**b**) Schematic diagram of three-way sensor. (**c**) X-direction swept test curve. (**d**) Y-direction swept test curve. (**e**) Z-direction swept test curve.  
original structure. But the mass of bionic optimized structure is 8.6 kg, which is far less than the original structure. The mass ratio reaches 23%. Benefiting from SLM, the complex optimized design can be rapidly manufactured. The vibration test of the bionic optimized structure indicates the eigenfrequencies of the vertical bracket are 309 Hz, 292 Hz, and 736 Hz, respectively. The maximum error rate of simulation and experimental results in the three directions is 4.2%. This combination of structural bionics and structural optimization forms a novel approach to design support structures in the Aerospace field. This work indicates that the combination of structural optimization, structural bionic, and additive manufacturing technology provides a powerful tool kit to the design of support structures.  
All authors contributed to the study conception and design. Data collection, three-dimensional model, and analysis were performed by [PERSON], [PERSON], [PERSON] and [PERSON]. The first draft of the manuscript was written by [PERSON] and all authors commented on previous versions of the manuscript. All authors have read and agreed to the published version of the manuscript.  
This research is funded by the National Natural Science Foundation of China (No. 51975246), Science and Technology Development Program of Jilin Province (YDZJ2021012 YTS134), Jilin Scientific and Technological Development Program (20200404149Y), the Ascl-zytsxm (202013), the Open Project Program of Key Laboratory for Cross-Scale Micro and Nano Manufacturing, Ministry of Education, Changchun University of Science and Technology (CMNM-K7202109), the Interdisciplinary Research Fund for Doctoral Postgraduates of Jilin University (No. 101832020 DJX052), and the Interdisciplinary Cultivation Project for Young Teachers and Students (No. 415010300078).  
Not applicable.  
The authors declare no conflict of interest.