Research Of Flexible Support For High-precision Bi-grids Of A Space Collimator

Space observation of the sun is one of the most important methods of astrophysics research,especially for the high-energy ray spectrum which is strongly absorbed by the earth's atmosphere,and the observation of these high-energy rays is of great significance for studying the formation mechanism of solar flares and the phenomenon of coronal magnetic reconnection.Hard X-ray Imager(HXI)is on-board the Advanced Space-Based Solar Observatory(ASO-S)satellite from one of China's sun observation program.Its scientific object is the hard X-rays produced by solar flares utilizing spatial modulation Fourier synthesis imaging technology.This technology is an indirect imaging technology based on a bi-grid collimator,and the key accuracy that affects its imaging quality is the alignment accuracy of the collimator bi-grids.Since a large-area bi-grid array is required for collimation,the supporting structure of bi-grid is a difficult point in the design.Large-area grid support base-plates are prone to large thermal deformation,and large base-plates cannot be split due to the requirements of precise assembly and adjustment.In this paper a sub-plate thermal stress relief solution based on flexible support is proposed.By dividing the entire base-plate with flexible support into small-area supporting sub-plates,the thermal stress of each part is prevented from affecting each other.For the support of the sub-plates,a support structure composed of inclined flexible blades in parallel is proposed,and its flexibility matrix and degrees of freedom are calculated based on the screw theory,which is also used to verify the effectiveness of the support structure.The flexibility matrix and the degree of freedom are then used to analyze the sensitivity of the dimensions of the flexure support.Combining the conclusions of former calculation and analysis,the response surface method(RSM)is used to optimize the design of grids support sub-plate and the size parameters of the sub-plate flexure support.On the base-plate with flexure support,a single sub-plate on it can reach a temperature adaptation range of ±5? while keeping the bi-grid offset error within 3?m,and the torsion error of the grating is within 2 arc seconds,and the temperature adaptation range of the entire substrate is increased to at least ±3.5°C,reducing the difficulty of base-plates thermal control.The offset error caused by the weight deformation of the base-plate does not exceed 5% of the total tolerance.And the 1st order natural frequency of the entire girds and base-plate assembly reaches 528.48 Hz,meeting the general mechanical performance requirements of space components.