| The image stabilization system of space astronomical telescope is divided into a coarse image stabilization system and a precision image stabilization system according to the range of the vibration frequency band.Precision image stabilization system generally controls the imaging light path by moving parts in the light to keep the light stable it can be considered as closed loop feedback control system in optical Path,Fine Guidance Sensor(FGS)is a rapid detection device for boresight error.The basic working principle of the FGS is to capture the stars in the FOV of the telescope and detect the error of the boresight.The ultra-long focal length of the telescope can be used to perform a high-precision measurement of the position of the boresight.The measurement precision and speed of the star on the focal plane of the FGS are two important indicators of the FGS.The measurement accuracy of the star spot directly determines the measurement accuracy of the relative error of the boresight.The speed determines the bandwidth of the closed loop feedback of the precision stabilization system.This paper focuses on the high-precision,high-speed measurement of the relative error of the boresignt of the space telescope,and builds a prototype to ensure the accuracy and real-time performance of the system.The main work of this paper is as follows: 1)Introduce the working principle of the FGS,analyze the star detection ability and the precision and speed of the FGS.Design hardware architecture and working mode of the FGS.2)The noise model of the image sensor,the system error model of the centroid location algorithm,the model of the influence of the optical axis vibration and drift were established,and the influence of each error source on the star centroiding accuracy is analyzed.3)In order to suppress the effect of noise on the centroiding accuracy,a 25th-order low-pass FIR filter was designed.A recursive background threshold segmentation algorithm is proposed for stray light interference,which can effectively extract effective star spots under nonuniform background without losing the energy of the star spot.4)Using the v-SVR support vector regression method for the system error,and the accuracy of the centroiding was improved.5)In order to improve the speed of star centroid extraction,a new star centroid extraction method is implemented in FPGA.6)Using the improved Radon transform algorithm based on gray-scale stretching and iterative blind restoration algorithm to recover the star spots,and improve the accuracy of dynamic star centroiding.7)A cascading self-organizing map(SOM)neural network algorithm model is proposed,which implements the star feature vector matching algorithm in hardware.8)An experimental system was built to verify the performance of the FGS.The experimental results show that the static measurement accuracy of the FGS is 1/32 pixel,the dynamic measurement accuracy is 1/25 pixel,and the measurement frequency is greater than 80 Hz.The major innovation of this paper is:1.This paper proposed a high accuracy processing technology for FGS with 2048 pixel×2048 pixel arrays,frame frequency greater than 80 Hz,high real-time performance,and high precision under complex conditions.Key technicals such as star detection capability,star map acquisition,star map preprocessing,and star extraction are analyzed and discussed.2.A FGS prototype was built.The filtering,threshold selection,and high-precision star centroiding algorithm were designed for FGS.The algorithm was implemented on the FPGA and the system processing speed was 80 Hz and the system was implemented with high integration and small size3.A ground verification device for FGS system was designed.The real-time performance of the star centroid extraction and the precision of dynamic and static star spot centroiding were tested.The test results showed that the static and dynamic star centroiding accuracy of FGS meets the simulation results... |
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