| Space technology is the embodiment of the modern science and technology level and comprehensive strength of a nation.As the core of space technology,aircraft navigation technology has become one of the key technologies research in countries all around.Global positioning system(GPS)should be the best choice for high-performance aircraft navigation,but with the deepening of the electronic fight and GPS's low availability in wartime,the accuracy and reliability of GPS in the military application cannot be guaranteed.In this case,the high performance SINS/CNS integrated navigation has an irreplaceable role in the strategy areas,such as high-performance aircraft,high-precision tactical weapons,etc.This paper is relied on the National Natural Science Foundation(61573113)and the city of innovative talent fund(2014RFXJ074)and researches the SINS/CNS integrated navigation technology and the star identification technology based on the ballistic missile.Based on introducing the commonly used coordinate systems,posture description parameters and the principle of SINS/CNS integrated navigation system and its subsystems,an integrated navigation model applied in the ballistic missile is built.Then,the working principle of star sensor and its technical index are expounded.According to the requirement of the star map recognition algorithm and in order to eliminate the redundancy matching in the process of identification,a navigation star table and a lookup table are built.Then the centroid segmentation method is adopted to achieve the high precision positioning of the star in image coordinate system,which prepares for subsequent star map recognition.Considering that the characteristic pattern of traditional grid algorithm can't reflect its internal similarity degree,which can affect the success rate of star map identification,therefore the metric function of concept is introduced into the grid algorithm,and a modified grid algorithm is proposed.The modified algorithm uses the metric functions derived from the characteristic patterns to reflect the similarity degree of different characteristic patterns,which solves the problem of feature extraction caused by the influence of the position error in traditional algorithm.A simulation based on the real situation is carried out.The results indicate that the star identification success ratio and the robustness of the proposed method are obviously superior to the traditional algorithm under the conditions of larger star position noise and the presence of artificial star,which shows the validity of the proposed method.Considering that traditional strap-down inertial/celestial integrated navigation system cannot accurately estimate the accelerometer bias,which can cause the divergence ofnavigation errors,a strap-down inertial/celestial integrated navigation method based on the stellar refraction sensing Earth's horizon indirectly is proposed in this thesis.The method is that starlight refraction angle which is got from the stellar sensor and the apparent height which is got from atmospheric refraction model are combined to inhibit the divergence of navigation errors.A novel measurement equation based on stellar refraction is developed and the relationship between the number of used refraction stars and navigation accuracy is analyzed.When multiple refraction stars are used,the proposed method can accurately estimate the accelerometer bias so that the position errors can be inhibited completely.The linear model of the integrated navigation system used in the ballistic missile is constructed based on the above principle,and its observability is analyzed.Finally,the estimation of the state of system is realized through the Kalman filter.The simulation results indicate that the precision of navigation based on the proposed method is better than that of the traditional method and is effective in inhibitings the divergence of the position error,which shows the validity of the proposed method. |
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