An optimal feedback guidance law with disturbance rejection objective is proposed for endoatmospheric powered descent.This guidance law with an affine form is derived by solving a novel problem called Endoatmospheric ...An optimal feedback guidance law with disturbance rejection objective is proposed for endoatmospheric powered descent.This guidance law with an affine form is derived by solving a novel problem called Endoatmospheric Powered Descent Guidance with Disturbance Rejection(Endo-PDG-DR).The key idea of formulating the Endo-PDG-DR problem is dividing disturbances into two parts,modeled and unmodeled disturbances:the modeled disturbance is proactively exploited by augmenting it as a new state of a dynamics model;the unmodeled disturbance is reactively attenuated in terms of its effect on the guidance performance by adjoining a parameterized time-varying quadratic performance index in the proposed optimal guidance problem.A Pseudospectral Differential Dynamic Programming(PDDP)method is developed to solve the Endo-PDG-DR problem,and correspondingly a robust neighboring optimal state feedback law is obtained,which has two synergistic functionalities.One is adaptive optimal steering to accommodate the modeled disturbance,and the other is disturbance attenuation to compensate for the state perturbation effect induced by the unmodeled disturbance.Using the derived feedback guidance law,a disturbance rejection level is quantified,and is correspondingly optimized by designing a quadratic weighting parameter tuning law.The numerical computations of interest are performed within a pseudospectral setting,ensuring polynomial analytical solution,high computational efficiency,and reliable convergence.展开更多
This paper addresses the challenge of mass uncertainty during the powered descent phase of a Mars lander and proposes a robust powered descent guidance algorithm that accounts for uncertainties in mass and fuel consum...This paper addresses the challenge of mass uncertainty during the powered descent phase of a Mars lander and proposes a robust powered descent guidance algorithm that accounts for uncertainties in mass and fuel consumption.First,the traditional trajectory optimization method based on convex optimization is improved by developing a fast and accurate solution approach using sequential convex optimization.Second,the effects of mass uncertainty on position are modeled and analyzed,with corresponding computational methods provided for different scenarios.Third,the worst-case scenario under mass uncertainty is analyzed through both geometric and theoretical approaches,and a modified glide-slope constraint method is proposed to ensure safe landing even in adverse conditions.Moreover,a closed-loop receding horizon based guidance is developed to further mitigate the effects of mass uncertainty and improve terminal landing accuracy.Finally,the proposed improved convex optimization algorithm and robust trajectory optimization algorithm are validated through simulation cases and compared with a probabilistic approach.The simulations further test various initial positions,velocities,and glide-slope angles,demonstrating that the solutions are both accurate and robust.展开更多
Compared with throttleable engines,constant thrust engines exhibit inherent advantages in architectural simplicity,operational reliability,mass efficiency,and lifecycle cost reduction.If using a constant thrust engine...Compared with throttleable engines,constant thrust engines exhibit inherent advantages in architectural simplicity,operational reliability,mass efficiency,and lifecycle cost reduction.If using a constant thrust engine can accomplish the lunar pinpoint landing,it would undoubtedly enhance mission economy.So,an adaptive constant thrust iterative convex programming guidance(CTICPG)is proposed for the multi-constraint propellant-optimal guidance problem for lunar powered descent with a unthrottled engine.First,the first-order hold(FOH)is used to discretize the continuous-time trajectory optimization problem.Then,to avoid the linearization error introduced by successive convexification,lossless and approximate convexification methods for constant thrust magnitude constraint,spherical gravity model,tilt angle rate constraint and final tilt angle constraint are presented.Subsequently,the lossless convex programming(LCP)algorithm is extended to obtain the CTICPG that can achieve lunar soft landing and pinpoint landing.Afterward,in order to enhance robustness and engineering practicability,the real-time estimation algorithm of engine parameters is introduced into CTICPG,thereby obtaining the adaptive CTICPG.Finally,numerical simulations are performed to verify the results,which show that CTICPG can achieve the soft landing and pinpoint landing.展开更多
This paper first introduces the technical requirements for autonomous flight, with a brief review of the International Academy of Astronautics(IAA) study group, "autonomous dynamic trajectory optimization control...This paper first introduces the technical requirements for autonomous flight, with a brief review of the International Academy of Astronautics(IAA) study group, "autonomous dynamic trajectory optimization control of launch vehicle". Two research scenarios, ascent rescue and powered descent, are compared from the viewpoint of optimal control. On this basis, the technologies on the autonomous trajectory planning and control under the thrust-drop failures in the ascending phase, and the autonomous guidance method during the powered landing for the recovery of the rockets are discussed respectively. For the ascending problem, the characteristics of different solutions, including the iterative guidance method(IGM)-based residual carrying capacity evaluation, the state-triggered indices(STI), the joint planning with the payload’s performance, and the multiple graded optimization(MGO), are analyzed for comparison. For the landing problem, the challenges such as the feasible region reduction caused by high thrust weight ratio(HTWR) and the disturbance adaptability brought by the limited feasible region, are studied in detail, as well as the onboard planning demonstration flight in China are introduced. Finally, the foundations supporting the above methods are summarized, which play an important role in promoting the flight autonomy.展开更多
This paper summarizes the autonomous guidance methods(AGMs)for pinpoint soft landing on celestial surfaces.We first review the development of powered descent guidance methods,focusing on their contributions for dealin...This paper summarizes the autonomous guidance methods(AGMs)for pinpoint soft landing on celestial surfaces.We first review the development of powered descent guidance methods,focusing on their contributions for dealing with constraints and enhancing computational efficiency.With the increasing demand for reusable launchers and more scientific returns from space exploration,pinpoint soft landing has become a basic requirement.Unlike the kilometer-level precision for previous activities,the position accuracy of future planetary landers is within tens of meters of a target respecting all constraints of velocity and attitude,which is a very difficult task and arouses renewed interest in AGMs.This paper states the generalized three-and six-degree-of-freedom optimization problems in the powered descent phase and compares the features of three typical scenarios,i.e.,the lunar,Mars,and Earth landing.On this basis,the paper details the characteristics and adaptability of AGMs by comparing aspects of analytical guidance methods,numerical optimization algorithms,and learning-based methods,and discusses the convexification treatment and solution strategies for non-convex problems.Three key issues related to AGM application,including physical feasibility,model accuracy,and real-time performance,are presented afterward for discussion.Many space organizations,such as those in the United States,China,France,Germany,and Japan,have also developed free-flying demonstrators to carry out related research.The guidance methods which have been tested on these demonstrators are briefly introduced at the end of the paper.展开更多
基金co-supported by the National Natural Science Foundation of China(No.62103014)。
文摘An optimal feedback guidance law with disturbance rejection objective is proposed for endoatmospheric powered descent.This guidance law with an affine form is derived by solving a novel problem called Endoatmospheric Powered Descent Guidance with Disturbance Rejection(Endo-PDG-DR).The key idea of formulating the Endo-PDG-DR problem is dividing disturbances into two parts,modeled and unmodeled disturbances:the modeled disturbance is proactively exploited by augmenting it as a new state of a dynamics model;the unmodeled disturbance is reactively attenuated in terms of its effect on the guidance performance by adjoining a parameterized time-varying quadratic performance index in the proposed optimal guidance problem.A Pseudospectral Differential Dynamic Programming(PDDP)method is developed to solve the Endo-PDG-DR problem,and correspondingly a robust neighboring optimal state feedback law is obtained,which has two synergistic functionalities.One is adaptive optimal steering to accommodate the modeled disturbance,and the other is disturbance attenuation to compensate for the state perturbation effect induced by the unmodeled disturbance.Using the derived feedback guidance law,a disturbance rejection level is quantified,and is correspondingly optimized by designing a quadratic weighting parameter tuning law.The numerical computations of interest are performed within a pseudospectral setting,ensuring polynomial analytical solution,high computational efficiency,and reliable convergence.
基金co-supported by the National Natural Science Foundation of China(No.U23B6001)the Natural Science Foundation of Heilongjiang Province,China(No.LH2022F023)the Fundamental Research Funds for the Central Universities,China(No.HIT.OCEF.2023009)。
文摘This paper addresses the challenge of mass uncertainty during the powered descent phase of a Mars lander and proposes a robust powered descent guidance algorithm that accounts for uncertainties in mass and fuel consumption.First,the traditional trajectory optimization method based on convex optimization is improved by developing a fast and accurate solution approach using sequential convex optimization.Second,the effects of mass uncertainty on position are modeled and analyzed,with corresponding computational methods provided for different scenarios.Third,the worst-case scenario under mass uncertainty is analyzed through both geometric and theoretical approaches,and a modified glide-slope constraint method is proposed to ensure safe landing even in adverse conditions.Moreover,a closed-loop receding horizon based guidance is developed to further mitigate the effects of mass uncertainty and improve terminal landing accuracy.Finally,the proposed improved convex optimization algorithm and robust trajectory optimization algorithm are validated through simulation cases and compared with a probabilistic approach.The simulations further test various initial positions,velocities,and glide-slope angles,demonstrating that the solutions are both accurate and robust.
基金supported by the Fourth Phase of the Chinese Lunar Exploration Programthe Civil Aerospace Pre-Research Project of China(Grant No.D040103)
文摘Compared with throttleable engines,constant thrust engines exhibit inherent advantages in architectural simplicity,operational reliability,mass efficiency,and lifecycle cost reduction.If using a constant thrust engine can accomplish the lunar pinpoint landing,it would undoubtedly enhance mission economy.So,an adaptive constant thrust iterative convex programming guidance(CTICPG)is proposed for the multi-constraint propellant-optimal guidance problem for lunar powered descent with a unthrottled engine.First,the first-order hold(FOH)is used to discretize the continuous-time trajectory optimization problem.Then,to avoid the linearization error introduced by successive convexification,lossless and approximate convexification methods for constant thrust magnitude constraint,spherical gravity model,tilt angle rate constraint and final tilt angle constraint are presented.Subsequently,the lossless convex programming(LCP)algorithm is extended to obtain the CTICPG that can achieve lunar soft landing and pinpoint landing.Afterward,in order to enhance robustness and engineering practicability,the real-time estimation algorithm of engine parameters is introduced into CTICPG,thereby obtaining the adaptive CTICPG.Finally,numerical simulations are performed to verify the results,which show that CTICPG can achieve the soft landing and pinpoint landing.
文摘This paper first introduces the technical requirements for autonomous flight, with a brief review of the International Academy of Astronautics(IAA) study group, "autonomous dynamic trajectory optimization control of launch vehicle". Two research scenarios, ascent rescue and powered descent, are compared from the viewpoint of optimal control. On this basis, the technologies on the autonomous trajectory planning and control under the thrust-drop failures in the ascending phase, and the autonomous guidance method during the powered landing for the recovery of the rockets are discussed respectively. For the ascending problem, the characteristics of different solutions, including the iterative guidance method(IGM)-based residual carrying capacity evaluation, the state-triggered indices(STI), the joint planning with the payload’s performance, and the multiple graded optimization(MGO), are analyzed for comparison. For the landing problem, the challenges such as the feasible region reduction caused by high thrust weight ratio(HTWR) and the disturbance adaptability brought by the limited feasible region, are studied in detail, as well as the onboard planning demonstration flight in China are introduced. Finally, the foundations supporting the above methods are summarized, which play an important role in promoting the flight autonomy.
基金Project supported by the National Natural Science Foundation of China(No.61773341)the International Academy of Astronautics Study Group SG 3.32。
文摘This paper summarizes the autonomous guidance methods(AGMs)for pinpoint soft landing on celestial surfaces.We first review the development of powered descent guidance methods,focusing on their contributions for dealing with constraints and enhancing computational efficiency.With the increasing demand for reusable launchers and more scientific returns from space exploration,pinpoint soft landing has become a basic requirement.Unlike the kilometer-level precision for previous activities,the position accuracy of future planetary landers is within tens of meters of a target respecting all constraints of velocity and attitude,which is a very difficult task and arouses renewed interest in AGMs.This paper states the generalized three-and six-degree-of-freedom optimization problems in the powered descent phase and compares the features of three typical scenarios,i.e.,the lunar,Mars,and Earth landing.On this basis,the paper details the characteristics and adaptability of AGMs by comparing aspects of analytical guidance methods,numerical optimization algorithms,and learning-based methods,and discusses the convexification treatment and solution strategies for non-convex problems.Three key issues related to AGM application,including physical feasibility,model accuracy,and real-time performance,are presented afterward for discussion.Many space organizations,such as those in the United States,China,France,Germany,and Japan,have also developed free-flying demonstrators to carry out related research.The guidance methods which have been tested on these demonstrators are briefly introduced at the end of the paper.
