On Time Optimal Control Of Soft Landing On Irregularly Shaped Asteroid

In recent years,with the continuous development of space technology,human beings have been exploring and utilizing outer space,including the moon and other celestial bodies in the solar system,especially the exploration of asteroids.The exploration of asteroids is conducive to the understand of the universe,the development and utilization of space resources and other important scientific values.In the dynamic modeling of the probe,most asteroids exhibit unsteady gravitational field,complex and irregular distribution as well as uncertainties of the model interfered by third party perturbations and other factors in the actual outer space environment due to their irregular shape and uneven density.The practical application of the detector has been challenged.In view of the above issues,considering the complexity of the space gravitational field of irregular asteroids,this paper proposes a new dynamic modeling method and the optimal control of spacecraft soft landing time is studied in depth.In this paper,the environmental factors and the characteristics of the asteroid are fully considered.Firstly,the boundary radius of the weak gravitational field is defined according to the complex irregularity of the weak gravitational field.The irregular asteroid is treated as a particle to calculate gravity outside the boundary radius,on the other hand,the polyhedron model is used to calculate the asteroid gravitational field within the boundary radius.Secondly,considering the small mass value of most of the irregular asteroids,this paper analyzes the effect of solar pressure and radiation pressure on the detector.Finally,the problem is transformed into a two-point boundary value problem(TPBVP)of Hamiltonian function by using Pontryagin's minima principle,and the numerical solutions of optimal trajectory and optimal control of the detector are obtained.Based on the new dynamic model,two irregular asteroids,Eros433 and Bacchus2063,are simulated respectively and the results are explored.The time optimal orbit strategy of the probe for soft landing of irregular asteroids can also accomplish the soft landing task well after dividing the boundary based on the complex gravitational field.Moreover,at the boundary radius of the gravitational field,the influence of the uncertainty caused by the model-free interference on the detector can be corrected according to the measured data of the detector.Furthermore,during the process of probe descent,the correlation values of energy consumption between the two models are not significantly different indicating a relatively small effect on the detector stems from the gravitational field of asteroid outside the boundary radius.Notably,under the same calculation conditions,the computer running speed is improved after dividing,which is more beneficial to realize the real-time control of the detector.