Study On Mars Aerocapture Guidance Methods

Mars exploration is the first choice for human beings to understand the solar system,study the origin of life in the solar system and make planetary exploration.Nowadays,all the space powers in the world have made Mars exploration missions such as Mars sample return mission and manned Mars mission,and actively prepared for it.Orbital design is one of the key technologies.Aerocapture using the atmosphere of Mars to decelerate and de-orbit the vehicle is an advanced technology that enables the vehicle to save fuel and rapidly enter the Mars parking orbit.The dissertation focuses on the Mars aerocapture and three guidance methods in Mars aerocapture.Firstly,in order to analyze the dynamic characteristics of the vehicle during the entire aerocapture process,based on the given Mars environment model and the configuration of the vehicle,through reasonable assumptions and approximations,combined with the aerocapture characteristics,built up the three degrees of freedom dynamic model which provides the necessary mathematical model for the design and analysis of the guidance algorithm.Secondly,based on the original Hybrid Predictor Corrector Aerocapture Scheme(HYPAS),the Mars aerocapture maneuver is divided into three phases,and the guidance law of each phase is obtained by reasonable assumptions and approximations.The simulation results show that the vehicle has good longitudinal control ability and lateral control ability in the atmosphere and can reach a predetermined apogee of Mars after exiting the atmosphere.Then,considering there are some assumptions and approximate processing in HYPAS,the dissertation developing the numerical predictor corrector which with less assumption.The Mars aerocapture guidance logic,which uses an enhanced version of numerical predictive correction,relaxes the phase change conditions and modifies the correction algorithm appropriately so that it can be used on low lift-drag ratio spacecraft.The simulation results show that the algorithm can be guided and the spacecraft can reach the predetermined target point.Considering the computational performance of on-board computers may not be able to meet the requirements of the predictive correction guidance method,the nominal trajectory tracking method is studied.Based on the backstepping method and the extended state observer,an adaptive sliding mode controller is designed based on the backstepping method.The sliding mode controller has a certain restraining effect on the jitter problem,and the result shows that the track can be well tracked.