Research On Guidance And Control For Soft Landing On Lunar At Main Braking Phase

It is one of the most important technologies for guidance and control of lunar soft landing at main braking phase. On the basis of summarizing the current work, the guidance and control methods for lunar soft landing at main braking phase were studied systematically by applying optimal control theory, which were under the requirements of autonomy, robustness and fuel optimization. The main contents are as following:Firstly, based on simplified lunar soft landing module, it educed an optimal locus module of the radial range, based on which polynomial explicit guidance law was designed. The simulation results indicated that the guidance law had robustness to influence of systematic parameter errors.Secondly, based on the optimal control theory, an energy optimal guidance law was obtained by solving the special two-point boundary value problem. Furthermore, there was a comparison between the two guidance laws mentioned above on systematic parameter errors influence on the guidance laws.Thirdly, after systematically analyzing the guidance and control system of main braking phase, attitude kinematics and dynamics of lunar vehicle at main braking phase were established. Given tracking rate and fuel consumption, mixed index tracking controller was designed by phase plane method based on the simplified attitude kinematics and dynamics module.Finally, the error modules were established. Sensor errors and initial condition errors which influenced the guidance precision were analyzed systematically. Sensitivity coefficient matrices can be generated by running directly analog program of guidance and control system, which can be used to provide ensemble statistical information concerning the performance of the main braking guidance scheme in the presence of sensor errors and initial condition bias inputs.