Research On Guidance Method And Load Relief Strategy For Boost Phase Of Low-altitude Missiles

In this thesis,we take missiles as our research object.In order to ensure the structural safety of the missile and reduce the impact of the low-altitude wind on it,a wind load reduction strategy based on the angle of attack feedback is studied.In order to meet guidance requirements,a missile online guidance method based on optimal control theory and a missile closed-loop guidance method based on Gaussian pseudospectral method are studied.Firstly,according to the engineering method of standard trajectory design,a standard program angle model is introduced based on Newton iteration method under given constraints.Considering the influence of wind,the mechanism of the wind affecting the missile's load is analyzed.The influence on the trajectory and the propagation mechanism of the wind influence are studied.By introducing the program angle correction coefficient and reducing the angle of attack,two wind load reduction strategies based on angle of attack measurement and estimation are proposed.Simulation results show that the load reduction strategy based on the measurement reduced the influence of wind by about 50%.Without increasing any measuring devices,the strategy based on the estimation can reach a similar result.Then,in order to correct the error caused by load reduction control,a missile online guidance method based on optimal control theory is studied.The optimal control model is established by simplifying the dynamic model of the missile boosting segment.Taking the terminal velocity of the missile as the optimization objective,we derived boost phase optimal guidance equations and solved the problem using shooting method.In order to achieve rapid launch and improve the adaptability to different missions,a missile online guidance scheme was proposed.The full-range trajectory of the missile was simulated and analyzed in combination with the wind load reduction strategy.Simulation results show that this guidance method is adaptable to different missions,and has a good robustness against interference.Finally,a closed-loop guidance method based on Gaussian pseudospectral method is studied.Based on the Gaussian pseudospectral method,the terminal speed of the missile is taken as the optimization objective,and the process constraints are introduced.Then the optimization model of boosting segment is established.In order to shorten the optimization time,initial trajectory guess,parameters homotopy and trajectory rapid re-planning techniques are studied.The closed-loop missile guidance process is designed and simulated in wind conditions.By contrast,the advantages and disadvantages of these two methods in this study are analyzed.Although the missile online guidance method based on optimal control theory cannot handle complex constraints,other techniques can be used to meet the requirements.This method does not rely on standard trajectory,and has high guidance precision,strong task and environment adaptability.It has broad application prospects.