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Research On Trajectory Planning, Guidance And Control Method For Planetary Landing

Posted on:2017-04-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:H J HuFull Text:PDF
GTID:1222330503955278Subject:Aeronautical and Astronautical Science and Technology
Abstract/Summary:PDF Full Text Request
Landing exploration and sample return from Planet is the major part of the deep space exploration missions. And planetary landing trajectory planning, guidance and control are the key techniques for achieving safe and precision landing. With support of the 973 program ‘Research on navigation, guidance and control for planetary landing’, the dissertation tries to reduce the fuel consumption and improve the landing precision on the conditions of multiple constraints, uncertain the landing environment, complex dynamics, and various surface configurations. The main contents of the dissertation are as follows:Firstly, the effect of the uncertain parameters to the landing errors is analyzed. Considering that the landing dynamics is uncertain, the linear covariance state equation is derived to express the error propagation equations. Then, the effects of the initial state uncertainties, the parameters uncertainties in the gravity and the body’s rotation rate and the uncertainties in thrust magnitude and direction are analyzed.Secondly, the trajectory planning method is studied. The optimal landing problem is transformed into the nonlinear planning problem by Gauss Pseudospectral method, and this avoids guessing the initial values. Considering the effects of the initial state errors, the closed-loop sensitivity matrix with respect to these errors is derived. By minimizing the fuel consumption and the sensitivity, the obtained optimal trajectory is desensitized to the initial errors. In addition, based on the error propagation equations, the tracking guidance strategy is involved to restrain the error propagation, and this improves the robustness of the landing trajectory.Next, the powered descent landing guidance and control methods are studied. By introducing the slack variable, the non-convex control constraint is relaxed, and the powered descent landing problem is solved by Second Order Convex Programming(SOCP). Moreover, the simplified sensitivity equation is constructed and augmented as the state equation, and the successive convex programming guidance method is presented. To explore the target site with complex terrains, the autonomous hazard avoidance control method based on navigation function is presented.Then, the autonomous control strategy of the spacecraft in the weak gravity is studied. Aiming at the unstable phenomenon of the spacecraft motion in the weak gravity, hovering control is achieved and the stable region is analyzed. For achieving the precision landing on asteroid, the autonomous control method with constant thrust based on Lyapunov method is derived. This can achieve the attitude and orbit control at the same time, and the control method is of analytical form, which can meet the requirement of real-time implementation.Last, the synthetic simulations for landing on Mars and asteroid are performed. The synthetic simulation software of Mars powered descent landing is developed, including the the terrain detection and guidance evaluation. The real-time simulation system for landing on asteroid based on dSPACE is used to verify the real-time implantation. dSPACE is used to generate the dynamics environment, and the PC104 computer is used to verify the guidance system in real time environment.
Keywords/Search Tags:Mars landing, attach to asteroid, trajectory planning, guidance and control, hazard avoidance
PDF Full Text Request
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