Nonlinear Control Methods For Flight Vehicle Attitude

In order to meet the needs of the development of aerospace enterprise, the task s of flight vehicles become more complicated and diverse, which puts forward higher requirements for the many control indicators of flight vehicles. The attitude control system provides important guarantee for flight vehicles to realize all kinds of complicated tasks. Because the spacecraft attitude control system has a complex coupling nonlinear characteristics and at the same time there are the influence of unfavorable factors such as system inertia uncertainty and the external environment torque, the design of attitude control system is a challenging and complex problem. The control accuracy of the flight vehicle attitude system is not only related with equipped hardware facilities, but also depends on the design of the attitude control method.Using the control system design methods of sliding mode control, dynamic surface control, adaptive control, finite time control and extended state observer(ESO), this paper proposed the corresponding nonlinear attitude control strategies to achieve the control purposes of flight vehicle attitude systems for the control design problems of attitude systems of rigid and flexible spacecraft and missile of swing nozzle as the actuator. The control designs are based on the theory of Lyapunov stability analysis.Accounting for the switching-type characteristic of attitude control actuators used in spacecraft three loop coupling attitude control systems, a large angle attitude maneuver control scheme of spacecraft is proposed. To avoid the singularity due to the use of Euler angle in large angle attitude maneuvers,the attitude kinematics of the spacecraft is described by quaternion. A variable structure controller with bounded inputs is designed by the method of Lyapunov and the stability of the system is proved. In order to avoid the chattering, a boundary layer is used to replace the sign function in the variable structure control law. The rest-to-rest attitude tracking control problem is simulated. Numerical simulation results show the effectiveness of the proposed attitude control method.The spacecraft attitude motion equations described by the Euler angles are described in vector form and viewed as two blocks, a kinematics block and a dynamics block. Based on Lyapunov stability theory, a robust dynamic surface control algorithm is designed for the nonlinear control system of attitude tracking of spacecraft in the presence of external disturbances. Then, the robust dynamic surface algorithm is combined with an adaptive update law such that the controller can be used when the inertial moments of the attitude control system are not known. Lyapunov analysis shows that this adaptive controller can also guarantee the asymptotical convergence of Euler angles. Finally, the effectiveness of the presented control algorithms is verified via simulations.The nonlinear attitude motion equations of flexible spacecraft described by the Euler angles are expressed in vector form. Based on dynamic surface control(DSC), a new robust dynamic surface sliding mode controller is proposed for the attitude tracking and active vibration suppression of flexible spacecraft in the presence of parameter uncertainty and external disturbances. Then, a novel robust dynamic surface finite time sliding mode controller is proposed with an extended state observer such that the uncertainties can be estimated. Lyapunov stability analyses show that the two controllers can guarantee the asymptotical stability of the attitude control system. The undesirable vibration of flexible spacecraft is also actively suppressed by the modal velocity feedback(MVF) approach. Finally, simulation results verified the effectiveness of the presented control algorithms.The nonlinear attitude motion equations of flexible spacecraft are described by the Modified Rodrigues Parameters(MRPs). Based on Lyapunov stability theory, a robust dynamic surface controller is designed for the attitude tracking and active vibration suppression of flexible spacecraft in the presence of external disturbance torques. Then, this controller is redesigned with an adaptive update law such that the controller can be used without the known inertial moments of the attitude control system. Lyapunov analyses show that the two controllers can guarantee the asymptotical stability of attitude control system. The undesirable vibration is also actively suppressed by the modal velocity feedback control method. Finally, simulations verified the effectiveness of the presented control algorithms.With the swing nozzle as the actuator of the missile attitude control system, this paper investigated three-channel attitude coupling control problem of the initial vertical launch of missile. A detailed attitude dynamics model of the missile with swing nozzle is established and then is combined with the attitude kinematics model denoted by Euler angles. Based on dynamic surface control technology, a new adaptive sliding mode controller is designed under the condition of aerodynamic parameter uncertainty, and a rigorous stability proof is given using the second method of Lyapunov. In order to avoid the chattering, the sign functions in the control law are replaced with saturation functions. Numerical simulation results verify the effectiveness of the proposed controller.