Engineering Application Research On Closed-loop Guidance In Launch Vehicles Ascent Stage With Terminal Attitude Constrained

With the continuous development of spacecraft and the increasing needs of space launch,the open-loop guidance gradually unable to meet the requirements of the flight mission now,the development and application of closed-loop guidance become an inevitable trend.The iterative guidance scheme in engineering application has the problem of large dispersion in injection attitude,which cannot meet the requirement of the tasks in which the payload needs fast orientation in orbit.In order to solve the problem of complex spacecraft trajectory optimization with multiple constraints in the future,this paper research on two kinds of closed-loop predictive guidance schemes aiming at the ascent in vacuum of the second stage of rocket with terminal attitude constraint,which is on the background of the application of new generation launch vehicle guidance system in China.In order to increase the dispersion in terminal attitude,this paper researches the scheme keeping the traditional iterative guidance scheme unchanged,adding an attitude-adjusting segment before reach destined orbit to obtain the target terminal attitude.On the basis of solving the optimal control solution via the indirect method,through the forecast the acceleration in attitude-adjusting segment and constant correct the apparent velocity needs to increase of the launch vehicle,finally realize the balance control of orbit precision and terminal attitude accuracy.The simulation results show that this scheme can meet the requirements of the terminal attitude and has good adaptability to the disturbance.The indirect method has difficulties in dealing with complex constraints and model switching tasks,then this paper studies a closed-loop predictive guidance method based on direct method.The second scheme based on simultaneous strategies("simultaneous method")to plan the trajectory and solve the feedback control variables,and closed-loop predictive frame is designed aiming at the changes of the task during the flight.Finally,the simulation results verify high precision of "simultaneous method" and the adaptability to disturbances of theclosed-loop predictive guidance scheme,and the real-time preliminary of the scheme can meet the requirement of engineering application.This method has great application prospect in more complex flight mission.