Reaserch On Guidance And Control Method Of Fixed Point Landing Of Vertical Takeoff Vertical Landing Rocket In The Last Stage

Reducing launch costs has always been a direction worthy of every astronaut.With the huge achievements made by Space X in the recovery of one-stage rockets in recent years,a significant reduction in rocket launch costs has become possible.The success of Space X confirmed the feasibility of reusable rockets.It can be said that recyclable rocket technology is an inevitable development trend.The fixed-point soft landing at the end of the rocket's return is a key part of the rocket recovery process.The reduction of dynamic pressure,the enhancement of atmospheric interference and the strict end constraints of the landing point increase the difficulty of guidance control design.This article sets a specific scenario for the problem of the vertical soft landing of the rocket returning to the last stage,that is,to achieve a vertical soft landing of a rocket with a flying height of about 3000 meters.The specific work of the thesis mainly includes:Firstly,modeling the precise dynamics of vertical soft landing rockets.Considering the earth's rotation and oblateness,the rocket's center of mass dynamic equation is established in the landing coordinate system,and the rocket's rotation motion equation around the center of mass is established in the arrow body coordinate system.This laid the foundation for the design of the following article.Secondly,considering the computational performance of the arrow-based computer and the accuracy requirements of landing,the fourth-order polynomial guidance was used to achieve the vertical soft landing of the rocket,which was verified by simulation.The performance of the guidance law under the conditions of atmospheric disturbance,wind influence and rocket performance deviation was verified by Monte Carlo simulation,and a reasonable end constraint was provided for the atmospheric deceleration section based on the simulation results.The Monte Carlo simulation results give the reachable area of the rocket under the conditions of initial position and speed determination.Thirdly,a nonlinear attitude control model for the vertical landing of the rocket is established.Aiming at the complex internal and external perturbations of the vertical landing stage rocket and the coupling between its position,velocity,and attitude,a non-singular terminal sliding mode control method based on interference observer is designed.The sliding mode observer is used to estimate the amount of interference,and the obtained estimate is used to compensate the controller.The simulation results show that the interference observer has a good estimation effect,and the controller can accurately track the command attitude.Finally,a six-degree-of-freedom simulation of the guidance control method for the vertical landing section was carried out to verify the comprehensive performance of the designed guidance control method systematically.