Research On Trajectory Optimization And Guidance Methods For Vertical Landing Of A Rocket

At present,the expendable multi-stage rocket is the main tool for human beings to reach the outer space.The technology of recycling and reusing the rocket can effectively shorten the launch cycle and reduce the cost of space launch.Some foreign aerospace enterprises have completed the recovery and reuse of the first stage rocket,and the relevant technologies have been quite mature.They can seize the international launch market with low launch cost,while the rocket recovery technology in China is still a long way to maturity.Rocket vertical recovery guidance is the key technology to realize the recovery of a rocket,and trajectory optimization is the basis for the research of guidance technology,so it is very necessary to carry out the research of rocket vertical recovery trajectory optimization and full range guidance method.The first stage recovery of the rocket starts from the separation of the first stage and the second stage to the end of the vertical landing.The whole process of rocket recovery is divided into sections,and the main tasks and things needing attention in each stage are described.The appropriate coordinate system is defined,the conversion relationship between coordinate systems is given,the influence of horizontal wind disturbance on aerodynamic force is considered,and the mass center motion equation of rocket vertical recovery is established.According to the research results at home and abroad,the simulation parameters of rocket recovery are given.They are the theoretical basis and parameter basis for trajectory optimization,guidance scheme design and simulation analysis.Based on the Particle Swarm Optimization(PSO)algorithm,the optimal nominal trajectory is designed by considering various constraints in flight and terminal constraints.In order to reduce the optimal result of the attack angle of the aerodynamic deceleration section,the strategy of selecting the terminal position of the aerodynamic deceleration section is proposed,and the appropriate terminal constraints are selected.The simulation results show that the dynamic pressure and normal overload are less than the maximum allowable value,the optimization result of the angle of attack of the aerodynamic deceleration section is smaller and the terminal state converges to the expected value.Newton's iterative method is used to solve the problem of guidance in the sections of adjusting course and decelerating by power,which can realize high-precision orbit change.A Proportional Differential guidance law in the aerodynamic deceleration section is proposed,which takes the command attack angle and the command sideslip angle as control variables,and can track the reference trajectory precisely in the aerodynamic deceleration section.The Fourth Degree Polynomial Guidance method is used to complete the guidance in the vertical landing section,and the estimation formula of the remaining time is given clearly,which speeds up the operation of the guidance algorithm.Considering the influence of many kinds of interference items,Monte Carlo simulation experiment is carried out to analyze the deviation distribution of three characteristic points: the start point of the aerodynamic deceleration section,the end point of the aerodynamic deceleration section and the landing point,and to verify the performance of the whole guidance scheme.