Research On Predictive Sliding Attitude Control For Hypersonic Cruise Vehicle

The near space hypersonic vehicle(HV) which has many outstanding advantages such as large flight envelope, high maneuverability and fast response ability compared with the ordinary aerocraft has attracted a growing worldwide interest. Due to the hypersonic velocity and changeable flight environment, the HV possesses some distinct dynamic characteristics of highly coupled control channels, serious nonlinearity, strong uncertainty and input saturation which all contribute to the design difficulty of the attitude control system with remarkable precision and strong robustness. For the purpose of tackling the attitude control problem, this dissertation carries out an intensive research on coupling compensation approach, fuzzy disturbance observer(FDO) and input saturation compensation approach based on predictive sliding mode control(PSMC) after analyzing the dynamic characteristics of HV. The main results in this dissertation are summarized as follows:To begin with, the six degree-of-freedom model of the HV is presented and the dynamic characteristics of HV is analyzed. Simulation is conducted to analyze the control coupling, motion coupling, inertia coupling and the influence of uncertainties and external disturbances, which points out the problems existing in the design of flight control system for HV.Then, to tackle the design problem of attitude controller, this dissertation presents a novel PSMC for HV by means of feedback linearization. First, the six rotational model of the HV is decoupled by using feedback linearization technology to facilitate the design of flight control system. Second, the sliding mode surface chosen as a combination of the tracking error and its higher order derivatives is predicted and incorporated into the quadratic performance index of the predictive control. The PSMC law with an explicitly analytical form could be derived by minimizing the performance index which attenuates the undesirable chattering phenomenon due to the switching of sliding mode control(SMC) law and avoids the large online computational issue of the predictive control. Moreover, a control coupling compensation approach based on control command compensation and the PSMC considering motion coupling and inertia coupling are proposed to solve the coupling problem in attitude controller design. Finally, simulation results demonstrate the effectiveness of the proposed attitude control scheme.Furthermore, this dissertation aims at further investigating the attitude control problem of the HV with system uncertainties, wind and external disturbances by presenting an improved fuzzy disturbance observer(IFDO) based on PSMC. First, for a class of uncertain affine nonlinear systems with uncertain model and external disturbances, we propose a FDO based on PSMC(FDO-PSMC) method. The composite disturbances containing system uncertainties and external disturbances are estimated by means of FDO. Afterward, to enhance the composite disturbance rejection performance, an improved FDO-PSMC(IFDO-PSMC) is proposed by incorporating a hyperbolic tangent function with FDO to compensate the approximate error of FDO. Finally, the proposed IFDO-PSMC is applied to the attitude control system design for the HV to track the guidance commands. Simulation results demonstrate the high precision and strong robustness of the proposed attitude control scheme.Finally, the PSMC for HV with input saturation based on fuzzy logic system is proposed. First, for a class of uncertain affine nonlinear systems with input saturation, we propose the PSMC scheme based on fuzzy logic system. To attenuate the influence of input saturation, fuzzy logic system is utilized to approximate the saturation property of control input and the adaptive law of fuzzy logic system is designed to guarantee effective approximation of the saturation property by means of Lyapunov stability theory. What is more, attitude controller considering input saturation, system uncertainties and external disturbances is designed by incorporating IFDO to combat the composite disturbances. Simulation results demonstrate the effectiveness of the proposed attitude control scheme.