Investigation On Ballistic Measurement And Technology Of Trajectory Reconstruction For Guided Projectiles

To improve the measurement accuracy of flight trajectory for guided projectiles so as to realize the correct trajectory control, some theoretical and technical problems regarding the ballistic measurement and trajectory reconstruction are analyzed and studied in this paper.Firstly, the rigid body equation of rocket projectiles is established. A nominal trajectory without considering any measurement errors is obtained via calculating the above equation numerically. On one hand, the nominal trajectory can provide on-board detecting devices with the evidence for generating the simulated data. On the other hand, the nominal trajectory can also be considered as the baseline when it comes to evaluating the accuracy of navigation system.The navigation algorithm of GPS system is analyzed and discussed. According to the technical parameters of a type of rocket projectile, the all-in-view positioning mode is chosen. The effect of applying the GPS on the rocket projectile is simulated and the corresponding results are analyzed. Various types of error resources occurring during the positioning of GPS are discussed. Both of the ionospheric delay error and troposphere delay error for measurement trajectory using GPS are simulated and the corresponding results are also analyzed.The problem of trajectory reconstruction is investigated using two types of nonlinear filter algorithms, namely EKF and UKF. An improved Extended Kalman Filter (IEKF) is proposed and it is applied to the problem of trajectory reconstruction. Theoretical analysis and simulation indicate that the time-consuming of IEKF is no more than that of EKF and is less than UKF. From the fidelity point of view, the accuracy of IEKF is equivalent to that of UKF and is much better than that of EKF. The result of trajectory reconstruction is of great satisfaction.Various types of disturbance resources during the flight of projectiles are analyzed. Considering the motion in the longitudinal plane during the passive phase for guided rockets as the research object, the longitudinal disturbance equation including disturbance resources is deduced and the aerodynamic coefficients formula is also fitted. The system state equation taking the interference source error of aerodynamic coefficients and GPS as the state variables is established. And the pseudo range of GPS is used as the measurement equation. The aerodynamic coefficients interference source in the longitudinal plane during the passive phase is estimated. And then the aerodynamic coefficients are identified so as to reconstruct the trajectory accurately.The principles of attitude measurement for projectiles using GPS single-antenna, twin-antenna and three-antenna are studied respectively. The application of the above three methods on measuring the projectile's attitudes is simulated. And the advantages and disadvantages of them are also analyzed. By comparing all the three methods comprehensively, also aiming at the characteristics of the research object in this dissertation, the integrated measurement mechanism using GPS twin-antenna plus inertial navigation system is proposed. The purpose of this mechanism is to obtain the flight state parameters for guided projectiles with high accuracy.The GPS/INS integrated navigation system taking the position, velocity and attitude information as observation variables is established. By adopting the Kalman filtering method, the capability of correcting the error of inertial navigation system using GPS attitude information is analyzed and simulated. The experiment and simulation results indicate that adding the attitude information under the integrated mode is able to improve the low-cost inertial navigation system. Not only does it improve the accuracy of position and velocity of inertial navigation system, but also enhance the precision of attitude greatly.