Guidance And Attitude Control Method For The Mars Atmospheric Entry

For future missions to Mars, it requires detector to have the ability to accurately land in a particular area. Environment of atmospheric entry phase is the worst during the Mars landing. Guidance and control of the detector not only directly affect the accuracy of parachute point, but also have an important impact on the final landing accuracy and even resolve the failure of the misson. This paper, on the background of high precision landing mission on Mars, aims at guidance and attitude control problems of the detector, studies the trajectory optimization and guidance and attitude control method, in the atmospheric entry phase. Numerical simulations and analysis also have been carried out.Firstly, this study analyzes Martian environmental parameters of the dynamics, shows the relevant coordinates and their convertions. And then the equations of orbital dynamics and attitude dynamics in the atmospheric entry phase are deduced and established, which are the basic of trajectory optimization and guidance control method.Secondly, considering the orbital motion dynamics and the constraints of entry phase, improved Gauss Pseudo-spectral method based on the standardized constraints is used to solve the trajectory optimization problem. During the optimization process, the control variable is bank angle, and the optimal trajectory should meet all kinds of constraints. Then, by using the ETPC of Apollo-derived Mars precision lander guidance, the optimal trajectory is tracked and the simulation results are analyzed.Then, for the low-lift-drag ratio lander with centroid biased way, this paper studies a predictive tracking guidance with modified parameter PID feedback-adaptive gain for Mars precision landing, whose variable is energy and features are maximum parachute deployment height and reducing the deployment error. The longitudinal predictive guidance, tracking guidance and lateral guidance of this law is designed, and the validity of the guidance law is verified by the numerical simulation results and analysis.Finally, for the attitude control problem in atmospheric entry, this paper gives a phase plane analytical method. A PD/D stabilized control law for angle-of-attack/sideslip angle and a optimal time-fuel usage control law for roll-axis are developed for atmospheric entry of Mars exploration missions, based on the analytic phase plane. The performance of the designed control law is demonstrated via simulations and analysis.