Study On Autonomous Celestial Navigation Algorithm And Its DSP Realization Of Near Earth Satellite

In recent years, celestial navigation has been applied much more widely in astronautic fields because of its high precision, high self-determination and low cost. It has become an important method of spacecraft autonomous navigation.This dissertation taking near earth satellite as research object, systematically studied the method of satellite autonomous celestial navigation based on multi-sensors, the application of nonlinear filtering method in satellite autonomous navigation system and its DSP realization. In addition, this dissertation also studied the display of DSP calculation results in graphics mode. The main work of this dissertation is summarized as follows:Firstly, a precise orbital dynamic model of near earth satellite is established in J2000.0 equatorial inertial coordinate system, considering the perturbation influence of earth shape perturbation, atmospheric drag, lunisolar perturbation and solar radiation pressure, etc.Secondly, the autonomous celestial navigation method is studied using measurement information of attitude sensors on the assumption that the near earth satellite has sun-sensor, earth-sensor and star-sensor simultaneously. The navigation filters based on EKF(Extended Kalman Filter) and UKF(Unscented Kalman Filter) are designed in order to determine the satellite's position and velocity. Numerical simulations are made in order to validate the feasibility of navigation scheme and evaluate the performance of navigation algorithms. In simulation section, this dissertation compare and analyze the performance of EKF and UKF algorithm, discuss the effects of sampling period and sensor precision on positioning accuracy.Thirdly, this dissertation studied the DSP realization of autonomous navigation algorithm. Transform the navigation algorithm program from computer into CCS(Code Composer Studio, TI's DSP IDE) using C and assembly language, and load the program into TI's TMS320C6713 chip through JTAG interface. When simulation experimentation is in operation, one computer transmit sensor data to DSP chip through RS232 interface in fixed sampling period. After receiving the needed data, DSP run on-board program and do real-time navigation operation. The simulation validated the feasibility of this navigation scheme and its results showed that using DSP chip to realize autonomous navigation algorithm has many merits, such as: high speed, high precision, etc. It can commendably meet navigation computer's requirements. At last, applying the LabLEW software resolve the question which is described as to display the DSP calculation results in graphics mode.