Autonomous Guidance And Control For Returning From Lunar Surface

One of the key technologies of human lunar exploration is lunar returningtechnology. Based on a deep understanding of the current situation of the field, the thisis expands the research on returning orbit design, ascending orbit design and guidanceand control. The main contents are as follows.For a short-term lunar visit task, the ascending cabin may fall out of the objectiveorbit plane, due to the lunar rotation. Therefore, it is necessary to execute the plane shiftinstruction to finish the orbital rendezvous. A solution is given on the minimum wedgeangle (the plane shift angle), as well as the formula of the global landing objective orbitobliquity and ascending orbit obliquity when the task is terminated with minimizedworst wedge angle.To optimize the lunar module ascending orbit, a dynamic model of the module isbuilt and nondimensionalized. Choosing the fuel usage as the index and usingPontryagin Minimum Principle, the problem is turned into the time-free “Two PointBoundary Value Problem”(TPBVP). Then based on an initial value guess method andforward scanning method, the TPBVP is sloved and the optimal ascending orbit isobtained.To solve the problem of complex calculation, bad real-time performance and weakadaptive capacity of fuel optimal guidance law, the closed-loop guidance law isdesigned using guidance method. First, dynamic equations of the ascending cabin arebuilt in the objective orbit coordinate system. Then the controlled variables areapproximated with polynomials Through the current state and final object state of thecabin, the coefficients of the expression are obtained and real-time guidance of theascending cabin is realized.To solve the large-angle flexible position control problem of the rigid bodyspacecraft, we first use the modified Rodrigues parameters to define the angularkinematic equations, then change the system equation to Brunovsky standard formusing exact feedback linearization method, and design a PID controller for the linearsub-system. We also adopted Pulse-Width Pulse-Frequency (PWPF) modulation on theconstant position-controlled engine, to implement the requirement of thrust control.To keep the angular position of liquid-filled spacecraft stable, a state feedbackcontroller is designed. Furthermore, we also design a sloshing mode observer and anoutput feedback controller to solve the sloshing mode fuzziness problem. In order totrack the angular position of the spacecraft, we use error quaternion to describe positionequation. Then combined with the sloshing mode observer, a dynamic output feedbackcontroller is designed. At last, for the saturation problem of the controller, the control parameters are adjusted by the gain scheduling method.