# Bionic Design of the Vertical Bracket of Wide Angle Auroral Imager by Additive Manufacturing
## 1 Introduction  
Light-weighting design is an extensively explored and utilized concept in aircraft, aerospace and mechanical engineering, especially in aerospace applications. In the least-weight and performance design, structural optimization is an effective method. Structural optimization is usually divided into three major ingredients: size optimization, shape optimization, and topology optimization [1; 2; 3]. The basic idea of topology optimization is to look for an optimal material layout in a given design domain with certain boundary conditions and constraints. Compared with size optimization and shape optimization, topology optimization has more degrees of freedom, allows for larger design space, and is one of the most promising structural optimizations [4; 5; 6]. It is usually used as a tool for finding efficient design concepts at the early design stage, whereas sizing and shape optimization are tools for detailed design at a later stage [7; 8; 9]. Recently, widely used in aircraft and aerospace field, optimization technology, particularly topology optimization,has become a highly effective tool to create innovative designs characterized by improved performance and reduced weights [10]. However, the results of topology optimization tend to be complicated and non-manufacturable. Therefore, the complexity of optimization results has become an obstacle to process and manufacture. The research objective of aurora detection is the dynamic changes of auroral radiation, which is very beneficial to prevent catastrophic space weather. In 1967, the world's first ultraviolet airglow spectrometer (UAS) was carried on the ogo-4 satellite launched by the United States, which opened the prelude of human space Aurora detection. In the following decades, countries have carried out the research and development of space-based ultraviolet imaging spectrometers, and obtained a large number of observation data. In November 2017, as the first space Aurora detector of China, the wide-angle Aurora imager (WAI) was launched on FengYun-3 D satellite, which filled the gap in the field of Aurora Observation in the far ultraviolet band. Generally, the structure of the wide-angle imager is designed according to the overall design requirements and experience, and the lightweight requirements are met by local hole removal and reinforcement. With the increasingly complex aerospace environment and increasingly harsh design conditions, traditional design methods are facing severe challenges [11; 12; 13]. Structural bionics sets up a bridge between biological structures and engineering structures. Drawing inspiration from the mechanical characteristics and special structures of organisms, structure behavior of existing engineered products can be improved. Researchers have conducted in-depth research on the practice of different organisms in nature in engineering [14]. [PERSON] et al. took the need stalks and bamboos with hollow stem node structures in nature as bionic prototypes. The structural characteristics of the stalk were extracted, and the design of the bionic tower was carried out. The results of finite element analysis and experimental verification shown that the structural rigidity and structural strength of the bionic tower and the prototype tower were improved [15]. [PERSON] et al. took [PERSON] as the bionic prototype to analyze the morphological characteristics and distribution rules of the leaf vein branch structure. They carried out a structural optimization bionic design for the distribution form of the internal ribs of the aircraft cover. The simulation results showed that the bionic type reduced the mass of the prototype cover plate and improved the specific strength, structural efficiency, and static performance [16]. [PERSON] et al. presented a new method of abstraction and specialization of natural microstructure for lightweight components by using topology technology. The combination of bionics in machinery provided a new theory and method of structural design for the design process [17].