Efficient, precise dynamic analysis for a complex spacecraft has become a research focus in the field of spacecraft dynamics. In this paper, by combining discrete time transfer matrix method of multibody system and finite element method, the transfer equations and transfer matrices of typical elements of spacecrafts are developed, and a high-efficient dynamic modeling method is developed for high-speed computation of spacecraft dynamics. Compared with ordinary dynamic methods, the proposed method does not need the global dynamic equations of system and has the low order of system matrix, high computational efficiency. This method has more advantages for dynamic modeling and real-time control of complex spacecrafts. Formulations of the proposed method as well as a numerical example of a spacecraft with a flexible solar panel are given to validate the method.
Any trajectory calculation method has three primary sources of errors, which are model error, parameter error, and initial state error. In this paper, based on initial projectile flight trajectory data measured using Doppler radar system; a new iterative method is developed to estimate the projectile attitude and the corresponding impact point to improve the second shot hit probability. In order to estimate the projectile initial state, the launch dynamics model of practical 155 mm self-propelled artillery is defined, and hence, the vibration characteristics of the self-propelled artillery is obtained using the transfer matrix method of linear multibody system MSTMM. A discrete time transfer matrix DTTM-4DOF is developed using the modified point mass equations of motion to compute the projectile trajectory and set a direct algebraic relation between any two successive radar data. During iterations, adjustments to the repose angle are made until an agreement with acceptable tolerance occurs between the Doppler radar measurements and the estimated values. Simulated Doppler radar measurements are generated using the nonlinear sixdegree-of-freedom trajectory model using the resulted initial disturbance. Results demonstrate that the data estimated using the proposed algorithm agrees well with the simulated Doppler radar data obtained numerically using the nonlinear six-degree-offreedom model.
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