Dynamic Modeling And Stability Analysis Of Launch Vehicle

The liquid launch vehicles effected by elastic vibration and the propellant sloshing makes serious impact on the aircraft attitude control system and body,therefore,modeling a proper dynamic model for the launch vehicle is basis of analyzing influence of various interference factors.Due to the fact that the nonlinear dynamic model of the launch vehicle is difficult to apply to the real-time stability analysis of the rocket there is important practical significance to develop a practical method of stability analysis for engineering.This paper establishes a nonlinear dynamic model toresearch the launch vehicles,which consider the influence of elastic vibration and liquid propellant shooting.Then the micro-deviation model is linearization of the nonlinear dynamic model based on the small disturbance.The transfer funcution of the body,obtained by calculating the eigenvalues of the characteristic polynomial with two step QR algorithm,is used to analyze stability based on the linear systerm’s stability criteria.Two-step QR algorithm is used to calculating the eigenvalues in engineering field,however it is hard to analyze stability timely without using the sparse of matrix to convergence quickly and calculate slowly with the needed ranks of elastic vibration and liquid sloshing growing,therefore it’s hard to satisfy demand of timely stability analysis.In view of the shortcomings of the two-step QR algorithm,an improved two-step QR algorithm is designed with using the asymmetric Lanczos decomposition to accelerate the convergence.This algorithm verified with simulation results can solve the high rank sparse matrix eigenvalues quickly and accurately and reduce the storage capacity with keeping the sparsity of the matrix.The method of stability analysis in this paper provides a new scheme and idea for the real-time stability analysis of the launch process of the launch vehicle,and has certain engineering application value,which proved to be feasible with analyzing the stability of the characteristic flight seconds of the example.