Research On Transfer Alignment Of INS/CNS For Hypersonic Vehicles

Hypersonic technology is a strategy commanding point in the field of aerospace technology in the 21st century. Hypersonic vehicles have many characteristics, such as high speed, strong penetration ability and so on. And hypersonic technology has become the strategic development direction of world’s military super powers. The responding speed of the weapon system and the accuracy of attacking the target are determined by the time and precision of the hypersonic vehicle weapon’s transfer alignment system. In this thesis, an SINS/CNS transfer alignment model is established in view of the practical application environment of hypersonic vehicles, including the linear model based on small misalignment angles, the nonlinear model based on large misalignment angles and the transfer alignment model based on additive quaternion. Kalman and Unscented Kalman filtering mathematic simulation platform are built to analyze the SINS/CNS transfer alignment system. The thesis contains the following aspects:(1) Space coordinate frames and the conversion relationship between coordinate frames involved in the transfer alignment technology of hypersonic vehicles are given. Basic theory, differential equations as well as error equations of quaternion are introduced. The hypersonic vehicle’s orbit design is given along with X-43’s test flight trajectory. And Simulink is used to simulate the orbit’s mathematical model.(2) After analyzing errors of the strapdown inertial navigation system, differential equations of misalignment angles, velocity errors, position errors, additive quaternion errors, velocity errors and position errors based on the form of additive quaternion are deduced under the launch point inertial coordinate frame. And after analyzing the error sources, such as inertial devices, flexure deformation and lever arm effect that influences hypersonic vehicles’ transfer alignment accuracy, mathematical models of these error sources are given.(3) Basic principles of star sensors and attitude decoding algorithms are introduced, and the algorithm of TRIAD and QUEST are deduced in detail. According to different attitude decoding algorithms, different forms of attitude information can be obtained. On the launch point inertial coordinate frame, the linear model based on small misalignment angles, the nonlinear model based on large misalignment angles and the model based on additive quaternion are established by using different forms of attitude information from star sensors.(4) The transfer alignment simulation platforms based on Kalman and Unscented Kalman are built to analyze the SINS/CNS transfer alignment model, and the simulation results verify the validity and practicability of the SINS/CNS transfer alignment system.