The Design Of Exo-atmospheric Biased Guidance And Precision Analysis

Fly-by approaching observation is one important method to monitor the space objects and to obtain their exact details. In order to guarantee the observation quality, the relative range and orientation between monitor vehicle and target at the fly-by moment must be controlled precisely. Based on this research background, the dissertation studies the design of biased guidance law, the precision analysis of biased guidance and its 6 DOF modeling and simulation. The major achievements attained are listed as follows.The biased guidance law is designed.(1)The proportional navigation reaches the zero miss distance by controlling line-of-sight(LOS) rate. Based on this idea,, the biased proportional navigation is designed in the LOS coordinate system, and the magnitude and azimuth of the expected biased zero effort miss distance(ZEM) are achieved by the mutual control effort in the horizontal and vertical planes of the LOS coordinate system.(2)Based the new concept of the target safe ty-area, the security characteristic of the biased proportional navigation is analyzed. Several conditions which threaten the target safety-area are found and the corresponding avoiding strategies are proposed.(3) The new biased guidance law in the LOS rotation coordinate system is designed, since there exist some security drawbacks of the traditional biased proportional navigation. And then the security problem is solved by controlling the magnitude and azimuth of ZEM separately.The Precision of biased guidance law is analyzed.(1) Based on CADET, the relationship between LOS rate estimation error and uncertainties of the LOS rate and ZEM are studied, the analytical solutions are deduced, which are used to analyze their propagation characteristics.(2) Regarding ZEM as the state variable, the relative kinematic equation is deduced, and then the analytical solution of the influence on the uncertainty of ZEM caused by the target maneuver is obtained by using C AD ET.(3) Based on the Unscented Transformation, the error transformation and propagation models are established, which are used to analyze the effects on the guidance accuracy caused by error factors such as the handover error, acceleration saturation and guidance dynamic lags and so on.The 6 DOF modeling and analysis of the biased guidance law are obtained.(1) The UKF model for the estimation of LOS rates is proposed. In order to compensate for LOS rate estimation delay, the compensation strategy based on the velocity feed-forward is proposed.(2) The 6DOF modeling of the biased guidance is built and the simulation is taken. The centroid dynamic equation and attitude dynamic equation are established.(3) The guidance precision of the biased guidance law under the influence of these error factors is analyzed, based on the simulation results.The biased guidance law designed in this thesis can achieve the expected magnitude and azimuth of ZEM, which is the control requirement of the fly-by mission. The conclusions resulted from the precision analysis based on CADET and UT have some guidance meanings theoretically for the application of this biased guidance law.