# Bionic Design of the Vertical Bracket of Wide Angle Auroral Imager by Additive Manufacturing
## 1 Introduction
As the only rigid support component, the skeleton of animal lower limbs has certain strength and stiffness in the process of movement [18]. At present, studies have been carried out on the long bone of lower limbs, from many aspects, such as the microstructure of bone [19; 20], the movement form of organism [21; 22; 23], the morphological and structural characteristics of bone [24], the change of geometric properties of bone section, finite element simulation analysis, and so on [25; 26; 27]. The above research was mainly aimed at the biological characteristics of the long bones of the lower limb, but the research on the optimization of aerospace support structure design combined with relevant characteristics had not been carried out yet. The emergence of additive manufacturing technology provides convenience for the preparation of complex structure. After more than 30 years of academic research and practical applications, AM had developed Stereolithography (SLA), Selective Laser Sintering (SLS), Selective Laser Melting (SLM), Fused Deposition Forming (Fused Deposition Modeling, FDM), and other technologies [28; 29]. The formable structural parts by AM range from micro-nano components to large-scale structural parts of several meters [30; 31; 32]. Additive manufacturing (AM) offers potential solutions when conventional manufacturing reaches its technological limits, including a high degree of design freedom, lightweight design, functional integration, and rapid prototyping. AM can solve a range of problems and improve production by customization, rapid prototyping, and geometrical freedom [33]. AM can be implemented not only for prototyping but also production using different optimization approaches in design, including topology optimization, support optimization and selection of part orientation, and part consolidation. [PERSON] et al. presented an electrothermal response optimization method of nozzle structure for multi-material RP based on fuzzy adaptive control (FAC). It eliminated the drawbacks of array nozzle clogging, stringing, and melt sagging, particularly in multi-material RP, by focusing on the electrothermal response so as to adaptively distribute thermal more accurate, rapid, and balanced [34]. [PERSON] et al. showcased a DOE methodology to optimize the SLM parameters to achieve fatigue performance as great as that of solid 17-4 Ph stainless steel [35]. [PERSON] et al. used the Taguchi method to optimize the printing factors to obtain the highest tensile strength of the printed PEEK object. The annealing effect on printed PEEK object and crystallinity were also investigated [36]. AM breaks through the shackles of traditional manufacturing technology with its powerful personalized manufacturing capabilities. Accordingly, it provides a solution for fabrication of structures derived from topology optimization and structural bionics. Here we introduce a new approach to design the vertical bracket of the wide angle auroral imager by a novel combination of structural bionics and structural optimization. Firstly, topology optimization is performed for the vertical support to find the optimal material layout and primary load carrying paths. Then, we study the morphological characteristics of femur and define the overall dimension of vertical bracket with reference to the width-to-diameter ratio of human femur. Next, the internal structure of the vertical bracket is designed on the basis of the distribution of bone mineral density. This provides fast, efficient way to determine the general shape and specific dimensions of the vertical bracket. Further, size optimization is utilized to obtain the optimal model. Thanks to Selective laser melting (SLM), the bionic optimized design can be rapidly manufactured. Finally, the superiority of the bionic optimization method is proved by the results of simulation analysis and vibration test. The rest of this paper is organized as follows. In Section 2, the original structure design of the vertical bracket is accomplished.