Research On Guidance And Control Technology Of Unpowered Autolanding For Reusable Launch Vehicle

The autolanding phase of Reusable Launch Vehicle is the last part of RLV’s demonstration flightand is the critical stage to complete the entire flight mission.This thesis mainly discusses about thetrajectory design and guidance-law design.The research of flight control system is based on its dynamics models and correspondingcharacteristics. According to the flight characteristics and Guidance task of RLV, thethree-freedom-degree models are built in order to lay the foundation for the upcoming research ofGuidance system, both with and without the presence of wind.Trajectory design is a key technology of Unpowered Approach and Autolanding Interface. Thetrajectory design method basing on altitude profile is formed using the nonlinear equations of motionin space. The velocity profile is planned reasonably along the altitude profile. The most difficult partof trajectory design bases on the velocity planning. The quality of the trajectory has direct influenceon the landing quality. The key parameters of trajectory are designed according to the flight task of theautolanding phase and the simulation algorithm and examples are given in this thesis. The trajectorydesign is a two-point boundary value question. Two kinds of drop-trajectory are discussed about basedon the previously designed trajectory.According to the different task in longitudinal-direction and lateral-direction, the altitude controland velocity control structure and the flight path control are designed, which will make the touchdownstates agree with the desired states, such as the touchdown velocity, sink rate, lateral deviation and soon.The simulation of robustness analysis is completed under the initial velocity uncertainty, initialposition uncertainty, the aerodynamic uncertainty and mass uncertainty. The results show that theguidance law is correct. The biggest drawback of the guidance system is its limited guidance area.Based on the single trajectory guidance system, we introduce the concept of multi-trajectory guidance.Finally, this thesis set up a simulation platform for RLV to carry out a Autolanding flight of thewhole process. A Monte Carlo simulation verifies the robustnesses of the Guidance system under theRLV’s uncertainty of aerodynamic, initial conditions and effect of horizontal wind, and the simulationresults show that the guidance and control strategy are rational and correct.