Design And Shape Adjust Of The Cable Net Structure For A Hoop Column Antenna

With the continuous development of aerospace technology,space mesh deployable antennas have shown a trend of large-scale and high-precision development.The hoopcolumn antenna has a simple deployment mechanism,light weight and high aspect ratio.It is one of the perfect construction forms for realizing large-diameter and ultra-large-diameter space mesh deployable antennas.In this paper,a hoop-column antennas is used as example to study the structure design,errors analysis and shape adjust of the mesh deployable antenna.(1)The design and pretension analysis of the cable net structure for a hoop-column antenna are studied.Firstly,based on the structural characteristics of the hoop-column antenna,the geometric topology of the reflector is designed by using a triangular and quadrilateral hybrid grid topology,and the influence of different segment numbers on the principle error is calculated,an appropriate segment number is selected according to the design accuracy requirements,complete the mesh geometric design.Secondly,the pre-tension distribution of the pure cable net is calculated based on the force density method.The two-step method is used to optimize the pre-tension of the boundary cable of the antenna considering the deformation of the truss.The results showed that the reflector of the cable-net can still maintain high accuracy under the effect of the pre-tension.The calculated pretension is applied to the finite element model for verification,and analyze the antenna mode.(2)The influence of the structure error of the mesh reflector antenna on the accuracy of the reflector antenna is studied.The uncertainty of manufacturing and assembly error causes changes in the tension of the cable net,which is one of the important factors affecting the accuracy of the surface accuracy of the reflector.Firstly,the calculation method of the shape and surface error based on the stochastic finite element method is studied.The explicit expression between the probability distribution of the random parameters of the reflector and the shape error is deduced,and it is applied to the influence of processing and manufacturing errors on the shape error of the reflector.Then the Monte Carlo simulation method is used to verify the methods this paper proposed.Finally,a calculation model including the cable length error is established,and the sensitivity of the tension cable is analyzed.It is found that the error of the length of the vertical tie cable has a greater impact on the accuracy of the antenna profile than the diagonal tie cable.The tension cables are sorted according to the degree of influence on the front mesh nodes,providing a reference for mesh adjustment.(3)A cable net adjust method that effectively combines the simulation model and machine learning is proposed.First,a finite element simulation model is established based on the structure parameters of the reflector,and the physical prototype is pre-adjusted based on experience.During the adjustment,the adjustment amount is applied to the simulation model for calculation at the same time,it takes the adjustment of the cable length as an input,and the coordinate difference between the simulation model and the physical model is output.The machine learning algorithm is used to establish the error prediction model.Which reveal the mapping relationship between the reflector node coordinate difference in the simulation model and the real model and the adjustment amount.The difference between the coordinates of the real prototype and the ideal shape is calculated,and calculate the cable segment adjustment by the multi-dimensional advance and retreat algorithm.Finally,use this method to adjust the accuracy of the hoop column antenna.Compared with the traditional adjustment method,the number of adjustments is greatly reduced,and it can significantly improve the accuracy of the surface accuracy.