| Star Tracker(ST)is widely used in high-precision positioning and navigation systems due to arcsecond accuracy and independence of orbital motion.However,the traditional ST cannot meet the needs of micro-satellite customization because of a large mass,volume,power consumption,and complex internal algorithm.Consequently the principle prototype of ST is developed to meet the requirements of micro-satellite.Therefore,this thesis summarizes the shortcomings of the previous research in the laboratory,designs and implements an ST which is suitable for micro-satellites.The thesis organizes as follows:Key indexes analysis.The key technical indexes of ST are analyzed according to the preset indexes:The selection criteria including an optical lens and image sensor is determined through analyzing the optical system of ST.Besides,certain constraints are applied in the electrical system to improve the performance to meet the requirements for the volume,mass as well as consumption of micro-satellite ST.Except that,the design of software algorithm is considered to meet the requirements of updated frequency.Hardware system design.The optimization design is carried out to improve the function and platform stability of the hardware system.The programmable logic device(CPLD)and core processor digital signal processor(DSP)are determined as the electrical structure.Besides,the image sensor of the advanced CMOS technology,and the optical lens are used as the optical structure.Finally,the hardware architecture of the whole system meets the requirements of the physical characteristics,electrical characteristics and computing power of ST.Software algorithm design and optimization.The system software is divided into three parts: DSP driver software is use for initializing the ST system,registering configuration of CMOS image sensor,and reading image data.CPLD driver software is used for collecting and storing the star map data,preprocessing the star map,and two out of three program loading of DSP.As the core part of the software system,DSP application software implementes star image segmentation,centroid location,star image recognition,star tracking and attitude solution.Futhermore,a star pattern recognition algorithm based on a master-slave star pattern is proposed,this algorithm has a reliable performance and takes less time to calculate in the tracking mode.Finally,the engineering design and verification are carried out in order to ensure the feasibility and reliability of the ST software system.Prototype test and analysis.Three-axis attitude measurement of the ST,image processing algorithm verification and algorithm running time test are completed based on the laws of celestial kinematics,which takes the precision of the earth rotation as the measurement benchmark.The results of real star observation indicate that the designed ST can meet the requirements of preset indexes.In conclusion,this thesis summarizes the shortcomings of the previous research in the laboratory and analyzes key technical indexes in the ST system.Beyond that,the hardware platform is optimized to improve the function of ST and a prototype is developed.At the same time,a test scheme based on the laws of celestial kinematics is determined as the software algorithm designing.The results of real star observation indicate that the designed ST meets the requirements.The research method in this thesis also provides a certain reference value for the further research on the micro-satellite ST. |
PDF Full Text Request