Guidance Law Design And Simulation For Mars Landing

With the development of deep space exploration, human space exploration hasalready exceeded the scope of the Earth-Moon system and its internal space. Due toits unique characteristics, Mars has become the most favorite target in deep spaceexploration. Among various exploration ways, soft landing is most valuable.Generally speaking, Mars landing can be divided into four stages: approachingphase, entry phase, parachute deceleration phase and power decent phase. For mostsuccessful landing missions, the main atmospheric entry mode is ballistic entry,which leads to a large landing deviation from nominal site. So it’s meaningful to domore research on Mars landing guidance.On the background of high precision landing mission on Mars, this paper has adeep research on the guidance in entry phase and power decent phase. The followingsections have been presented:Firstly, some approximate and reasonable assumptions are made for thedynamic characteristics of the Mars probe landing phase. Then the dynamic modelof Mars entry phase and power decent phase are set up, which provide essentialmathematical models for the subsequent guidance law design.Transform the nominal trajectory planning of probe entry phase to the solve ofoptimal control problem, due to the strong nonlinearity of co-state equation, theanalytical solution cannot be obtained in the two-point boundary value problem withthe Pontryagin minimum principle. So this paper transforms the optimizationproblem to nonlinear planning problem with Legendre pseudo-spectral method. Inorder to make the entry trajectory meet different performance requirements, thispaper introduces a kind of scoring mechanism, which is the base of open umbrellapoint selection scheme. For the sake of overcoming impact of uncertain parameter inentry phase, an adaptive sliding mode guidance law based on neural network isadopted, making the guidance and control system has strong robustness.Finally, a nominal trajectory planning and guidance law in power decent phaseare developed. Based on the designed nominal orbit, terminal sliding-mode guidancelaws are developed. The effectiveness of the guidance laws are verified meanwhile.