Research On Trajectory Optimization And Three-Dimensional Guidance Technology For Re-entry Vehicle With Complex Constraints

The reentry vehicle can undertake varieties of missions,such as the round-trip between the earth and the space,the near-earth reconnaissance and the long-distance,fast and high-precision strike,which has a very high application value in the aerospace and military fields.This paper aims at the critical technologies in multiple constraints trajectory optimization and the return guidance problems of a class of middle and high lift-drag ratio reentry vehicles,working on the entry trajectory optimization and footprint analysis based on SCP method,hybrid predictor-corrector guidance based on optimized way-points and the integrated TAEM and A&L phase on-line guidance method.The main results achieved are summarized as follows:The trajectory optimization of the reentry glide vehicle has the characteristics of multiple constraints and complex nonlinear dynamics.Under the influence of high-speed motion and high lift-drag ratio aerodynamic,the control variables and flight states are highly coupled,which makes the trajectory oscillation and difficult to converge and reduce the efficiency and quality of trajectory optimization.In order to solve this problem,an optimization algorithm which combines the reduced order dynamic model with the sequence convex program method is proposed.In this paper,the transformation method of constraint conditions and the convexification method of optimization problem under the reduced order model are studied.The factors affecting the reachable region are analyzed,and the dynamic reachable region along the waypoint is calculated.The piecewise convex optimization method is proposed to solve the problem of reverse of reentry vehicle’s bank angle,and the method is used to solve the optimal reentry trajectory under the constraint of no-flight-zone.The simulation results show that the introduction of the equilibrium glide condition not only reduces the order of the dynamic model,but also improves the difficulties of trajectory jump and convergence caused by the high lift-drag-ratio in the optimization process,and the smoothness of the trajectory is ensured.The algorithm based on the combination of reduced order model and sequence convex optimization can converge to the optimal solution by 4-8 times of iterations with second level,which improves the speed of trajectory optimization.For the case of the avoidance of the multiple no fly zones during the middle flight of a re-entry glide vehicle,the existing re-entry guidance methods is difficult to meet the constraints of re-entry corridors and terminal states effectively,and at the same time to achieve the global optimal selection of the evasion path,which leads to the degradation of overall performance of the maneuvering flight path.In order to solve the problem of high-quality maneuvering trajectory generation and high-precision evasion guidance,a hybrid guidance strategy based on waypoint optimization and three-dimensional analytical predictior-corrector method is proposed.The guidance problem is divided into two sub-problems: waypoint optimization and waypoint tracking guidance.In order to solve the problem of fast generation and high accuracy prediction of long-distance three-dimensional constraint trajectory of high lift drag ratio vehicle in the two subproblems,aiming at the shortcomings of current numerical prediction methods,such as low efficiency,sensitivity to model parameters and poor accuracy of long-distance prediction of conventional analytical prediction methods,a recursive segmented three-dimensional analytical prediction method is proposed based on the reduced order model,which makes the long-distance prediction more accurate.When the prediction error of landing point is less than 1%,the prediction time is about 0.01 second.Then the prediction method is combined with particle swarm optimization to optimize the waypoints sequence considering the constraints of reentry corridor and multiple no fly zones,which reduces the range and control cost of reentry trajectory under complex constraints.Aiming at the problem of waypoint tracking and guidance with high precision,an improved recursive three-dimensional analytical prediction method and multi trajectory parameter local correction guidance strategy are proposed.Numerical simulation for multiple reentry tasks and disturbance of initial conditions and model parameters is carried out to verify the performance of the proposed guidance method.The results show that the combination of the improved recursive piecewise analytical prediction method and local correction guidance strategy can adapt to the disturbance of large-scale initial conditions and model parameters,and ensure that the reentry constraints are met.The terminal position error for different guidance tasks is less than 5km,are superior to the conventional two-dimensional analytical predictior-corrector reentry guidance law.The reusable lauch vehicle is difficulty to guarantee the landing safety and accuracy under the influence of extreme handover state dispersion and model deviation during the low speed unpowered horizontal landing process.In order to improve the efficiency,precision and adaptability of trajectory prediction of energy management and landing phase,and improve the flexibility of guidance trajectory,the integrated on-line guidance method for TAEM and A&L phase is proposed,and the integrated three-dimensional online guidance framework is constructed.Based on the parametric dynamic pressure profile,height profile and ground geometry,the integrated longitudinal and lateral trajectory is described.Considering the influence of lateral motion in the design of dynamic pressure profile,the three-dimensional trajectory information database is obtained offline.Aiming at the problem of online high-precision prediction of integrated range-to-go,considering the influence of model deviation and lateral motion on the prediction accuracy,a fast trajectory prediction method is proposed,which combines the piecewidth look-up data table method with online range estimation correction.Multi trajectory parameters updating strategy under constraint conditions is proposed to solve the problem of coordinated updating of multi trajectory parameters,which can enhance the ability of trajectory adjustment and ensure the margin of parameter updating and the suitability of trajectory.The dynamic inverse control method is used to track the longitudinal and lateral trajectory accurately.The numerical simulation shows that the integrated online guidance algorithm can flexibly adjust the trajectory parameters and turning mode according to the initial conditions and model changes.The proposed trajectory prediction algorithm takes into account the additional energy consumption of lateral maneuvering and online observation and correction of the range changes caused by model deviation,which greatly improves the trajectory prediction accuracy of trajectory prediction,the landing accuracy is kept at meter level in case of large changes in initial position,heading and energy,and the time of single trajectory prediction is less than 2.6ms.The guidance system can respond to the model deviation caused by the control surface failure and other factors in real time without directly identifying the model parameters online and dynamically adjust the trajectory parameters to ensure that the landing accuracy requirements are met under the influence of model deviation.