High-Precision Fault-Tolerant Attitude Control For Complex Spacecraft

The high precision attitude control of complex spacecraft with large flexible appendages is a hot issue of research in the field of aerospace. Due to the coupling interference of the rigid body and flexible appendages, model uncertainty, input saturation and actuator faults, etc., the high precision attitude control of complex spacecraft faces with huge challenge. In order to supply a gap that zero order approximation model can not well reflect the dynamic characteristics of deformation of flexible appendages, the first order approximation model is employed to establish a complete model of spacecraft with flexible appendages. Meaningwhile, the coupling of rigid body and flexible appendages, and geometric stiffening effect of flexible appendages caused by rapid angle maneuver are analysed in detail.Model uncertainty mainly includes inertia matrix uncertainy and modal parameter uncertainy of flexible appendages. 1) For the identification of the inertia matrix of spacecraft in orbit, A error-in-variables(EIV) system based on the moment of inertia parameters is established. Considering the noises of the input/output of the system may be colored and correlated, higher-order cumulant-based least square methods are proposed. Convergence analysis of the higher-order cumulant-based recursive least square(HOCRLS) is conducted by using the stochastic process theory and the stochastic martingale theory. It indicates that the parameter estimation error of HOCRLS consistently converges to zero under a generalized persistent excitation condition. 2) For the identification of modal parameters of the flexible appendages, Observer/Kalman Filter Identification Algorithm(OKID) is employed to identify the modal parameters of the flexible appendages in orbit. As the angular acceleration of the spacecraft boby is only used as the input of the system to identify, an external disturbance caused by additional signals could be avoided.The main bottleneck of high precision attitude control of complex spacecraft includes model uncertainy, external disturbance, input saturation and actuator faults, etc. In order to improve the precision of the attitude control of spacecraft, the following issues are mainly studied in this thesis: 1) For model uncertainy and exteral disturbance of flexible spacecraft, an inverse optimal attitude controller is designed based inverse optimal approach and unit quaternion representation of attitude by the reconstruction of Lyapunov function. Next, an anti-unwinding inverse optimal attitude controller for flexible spacecraft is designed to avoid the issue of attitude slewing unwinding due to the double values of unit quaternions. These proposed attitude control methods can achieve H? optimal control without the need to solve the Hamilton-Jacobi-Isaacs Partial Differential(HJIPD) eaution. 2) For the issue of input saturation, actuator amplitude constraint and, actuator amplitude and rate constraints are considered at length, respectively. Two novel constrained attitude controller, one accounts for actuator amplitude constraint and the other considers actuator amplitude and rate constraints are designed. A new saturation compensator is designed and embedded into the controllers to eliminate the effect of actuator saturation. The proposed controllers can achieve Input-to-State Stable(ISS) subjected to input saturation. In order to avoid the issue of attitude slewing unwinding due to the double values of unit quaternions, two anti-unwinding constrained attitude controllers for flexible spacecraft are also designed. 3) To handle the spacecraft system with actuator faults and input saturation, an amplitude constrained fault-tolerant attitude controller and, an amplitude and rate constrained fault-tolerant attitude controller are designed, respectively. Three kinds of actuator faults: partial loss of effectiveness of actuator, stuck fault and outage of actuator are considered in this thesis. A new Lemma is first proposed and rigorous proof is presented. By introducing two parameters undate laws to estimate the unknown parameters caused by actuator faults and by designing saturation compensator to be embedded into the controllers to eliminate the effect of actuator saturation, the proposed constrained fault-tolerant contollers can achieve ISS in the presence of input saturation and actuator faults. The proposed controllers need not the prior knowledge of actuator faults. In order to void the issue of unwinding, an anti-unwinding amplitude constrained fault-tolerant attitude controller and, an anti-unwinding amplitude and rate constrained fault-tolerant attitude controller are also designed, respectively.Simulation results are presented to assess the performance of the proposed methods in this thesis.