Close-range Relative Navigation And Integrated Attitude/Position Control Methods For Elliptical Orbit

The autonomous proximity operation mission for two spacecrafts is selected as the background,and the close-range relative navigation and integrated attitude/position control methods for elliptical orbits are studied in depth.All of the proposed methods are suitable for circular or near circular orbits.The main results achieved in this dissertation are summarized as follows:The relative position and attitude estimation method based on static geometrical relation of the beacons is studied.The Modified Rodrigues Parameters(MRPs)is selected as the attitude representation,and the VISNAV measurement model 1 is derived using MRPs.The nonlinear least squares method is adopted to determine the relative position and attitude,which can provide the initial values for the subsequent designed navigation filter.Both beacon location error noise and VISNAV measurement noise are taken into consideration.The measurement-error covariance matrix is derived and used in the estimation method.Simulation results indicate that the beacon location error noise has rather large effects on the relative position and attitude estimation.As the distance between two spacecrafts becomes close,the observability of the system is improved and the estimates will be more and more accurate.The close-range relative navigation techniques using state estimation method are studied.Based on VISNAV measurement model 2,a novel relative spacecraft position and attitude estimation approach based on extended Kalman filter(EKF)is derived.Compared with the traditional algorithm,this approach is to additionally estimate the attitudes of both spacecrafts relative to the chief's Local Vertical Local Horizontal(LVLH)frame,so that the simplified assumption that the chief's body frame coincides with its LVLH frame is removed.In essence,the attitudes of the chief spacecraft need not be known a priori.Further,a novel relative spacecraft attitude and position estimation approach based on cubature Kalman filter(CKF)is derived.A modified version of the CKF is presented based on the averaging-quaternion algorithm,which improves the filtering performance to some extent.It is assumed that the tumbling chief spacecraft may be in failure or out of control and there is no a priori rotation rate information.A relative position and attitude estimation approach is presented for the tumbling chief spacecraft.The inertia ratios are introduced to solve the unknown chief inertia parameter circumstance.When three or more beacons are present,the proposed algorithm provides accurate estimates of relative attitude,position,velocity,deputy gyro bias,as well as chief angular velocity and inertia ratios.a As the number of beacons increases,more accurate relative attitude and position information is provided in general.The integrated position and attitude control method based on dual number is studied.The dual-number-based spacecraft kinematics and dynamics models are formulated,and the relative error dynamics equations based on dual number are further derived.It has been proven that these equations are the same with the traditional relative rotational and translational equations.The integrated position and attitude control method based on dual number is designed,and the global asymptotical stability is demonstrated using Lyapunov theory.The all-thrust integrated position and attitude control system is designed,and the control allocation algorithm is proposed to solve this linear programming problem.Simulation results indicate that the proposed integrated attitude/position control method is effective,and has well-behaved robust to the mass and inertia uncertainties in addition to external disturbances.Two high-precision attitude maneuver control methods are studied.For the control moment gyros(CMGs)actuated spacecraft,an attitude maneuver control approach combined with optimal attitude trajectory planning method and linear quadratic regulator(LQR)method is presented.Both the fixed-time energy-optimal and synthesis performance optimal cases are taken into account.The corresponding nonsingular attitude maneuvering trajectories(i.e.,open-loop control trajectories)with the consideration of a series of constraints are generated via Radau pseudospectral method(RPM).In addition,a LQR closed-loop controller is designed to eliminate the error effects of initial errors,inertia uncertainties and external disturbances.For the parameter uncertainties and external disturbances,a model error predictive control(MEPC)algorithm is further studied.This method uses a predictive filter to estimate the model errors,which can compensate the model errors and external disturbances effectively.