Gravity Anomaly Compensation-Oriented Trajectory Planning Approach For Hypersonic Glide Vehicles

The error propagation mechanism and perturbation compensation strategy for the gravity anomaly impacting on glide trajectories are focused on,involving the issues of 1)drag-acceleration based glide trajectory planning algorithm with multi-constraints,2)influences of gravity anomaly on glide trajectory planning,2)error propagation algorithm for gravity anomaly on glide trajectories,4)local representation of gravity anomaly along flight trajectory,5)perturbation-compensation-oriented glide trajectory correction strategy.The efforts of this dissertation struggle to close the gaps of these problems mentioned above in theory foundation,method supporting,data accumulation and mechanism recognitions.The main contributions are as follows.1.Drag-Acceleration Based Glide Trajectory Planning Algorithm with Multi-Constraints.A transposed-pole coordinate frame is redefined to simplify the trajectory planning.Both of the dynamic models for entry formulation in the half-speed coordinate frame and the transposed-pole coordinate frame are developed.The transformation relationships of the flight state variables between the half-speed coordinate frame and the transposed-pole coordinate frame are presented.The multi-constrains considering No-Fly Zones and Waypoints are modeled and the corresponding flight corridors are deduced.Based on these models,the glide trajectory planning algorithm considering multi-constrains based on the D-E?drag acceleration versus energy?profile is developed.Simulation results indicate that a feasible glide trajectory meeting multi-constraints can be generated efficiently and tracked effectively.2.Influences of Gravity Anomaly on Glide Trajectory Planning.The influences of the gravity anomaly in flight impacting on the glide trajectories with different initial azimuth angles,changed reentry points and different down-ranges are simulated.The deviations of drag accelerations,bank angles,terminal positional states and terminal velocity states are analyzed.Computational models of gravity anomaly with different truncation errors are employed in the simulations.Qualitative and quantitative recognitions for the influences of gravity anomaly on the glide trajectory planning are achieved.The analysis results supply the theory foundation and data supporting of the perturbation compensation strategy.3.A Ballistic Error Propagation Algorithm and Its Corresponding Analysis Method for Glide Trajectory Based on Perturbation Theory.A ballistic error propagation algorithm for glide trajectories is originally proposed based on the perturbation theory.The corresponding error propagation algorithm and analysis method are developed.Perturbation equations which treat perturbations as external inputs and flight state deviations as state variables are established.Based on logic simplification assumptions,the analytic expression of the state transition matrix is deduced and thus the ballistic error propagation model is established.The transposed coordinate frame is introduced to simplify the development of the perturbation equations and the error propagation model.By employing the gravity anomaly as the single perturbation factor,the proposed algorithm is validated and verified by numerical experiments.Being compared with the traditional method,the proposed method takes only just a quarter computational costs and restrains the method errors beneath 10%of the total terminal deviations.It is an effort that initially focuses on the error propagation mechanism of the glide trajectory and the proposed model has sufficient precision for the analysis of modeling deviations,thus laying the foundation of correcting the modeling deviations and enhancing the accuracy of vehicle's flight states.4.A Local Representation of Gravity Anomaly along Flight Trajectory and Its Corresponding Fast Approximation Scheme.An extension local representation and its corresponding fast approximation scheme for the computation of the gravity anomaly along glide trajectories are initially proposed.To meet the needs of temporary mission changes,the mathematic model for the tridimensional envelope of glide trajectories is deduced,and thus developing a universal envelope by dividing the domain and assigning values to the nodes.To lighten the computational burden,a local channael model is reconstructed by acquisiting the data of nodes for the three-level extension cells which the planned trajectory flies through.The multi-gridded scheme restrains the actual glide trajectory from flying beyond the channel while the extension approximation achieves a high-fidelity computation of the gravity anomaly.Simulations indicate that the approximation precision of the extension method is over an order of magnitude higher than that of the non-extension method.The terminal positional deviations of glide trajectories due to approximation errors are beneath 100m on the partitioning schemes of 10km/2°/2°.By using this scheme,it just needs 948 memorized data and 14.023s to achieve the model reconstruction.In the computation of a glide trajectory containing 10000 calculation points,the onboard computational time for the proposed method is only 6 thousandth of that for 1080-order Spherical Harmonics.5.A Fast Perturbation-Compensation-Oriented Glide Trajectory Planning Correction Strategy.An efficient trajectory planning correction strategy and its corresponding algorithm for the glide trajectory are initially proposed to compensate the deviations due to perturbations which can be determined beforehand.The proposed strategy evolves the traditional acceleration-based trajectory planning into a high-fidelity one with perturbation compensations by correcting the parameters of C₁ and C₂,which are named planning data and can modify the drag profile.To derive the mathematic representation of the terminal state deviations induced by perturbations,the ballistic perturbation theory is employed to develop the error propagation model for the glide trajectory.The semi-analytic mathematic relation of the planning data correction quantities and the terminal state deviations are deduced in a transposed coordinate frame.Taking the gravity anomaly along a glide trajectory as the single perturbation factor,the performance of the proposed method is validated and verified.The simulation results indicate that the corrected planning outperforms the traditional one,with a reduced terminal positional deviation of about 1km and 10²0 times enhanced terminal precision.The semi-analytic representation of the correction quantities with respective to the perturbations allow it to reveal the error propagation mechanism and thus restrain the perturbation deviations.Furthermore,the application of this proposed correction strategy can be expanded into other single or multiple predetermined perturbations efficiently and effectively.