Research On Attitude Control Method For Hypersonic Cruise Vehicle

This thesis researches on advanced control methods, such as dynamic inverse(DI), sliding mode control(SMC) and model predictive control(MPC), for hypersonic cruise vehicle(HCV). The model of HCV is fast-variability, strong coupling, highly nonlinear and includes uncertain parameters. Based on integrated guidance and control design, the Six Degrees of Freedom(Six-Do F) simulation studies demonstrate that the advanced control methods are robust with respect to the outside interference and parametric uncertainties, and meet the performance requirements with acceptable control inputs.Longitudinal model and Six-Do F motion model of HCV are being developed for control studies. When DI decoupling technology is applied to the longitudinal model and rotational motion dynamic model, respectively, the relative degrees both equal to the model system’s order. Thus, the longitudinal model and rotational motion dynamic model both can be Input/Output linearized completely and decoupled, which are proved by simulation studies.To combined robustness with decoupling and improve the performance of control system, two new SMC methods are proposed based on DI control method. One of the two new methods is a parametric command method, which is proposed based on the normal SMC method. To improve the dynamic response ability of the attitude control system, this new method uses attitude angle’s current value and attitude angle’s command to calculate the attitude angular velocity’s command, which is self-correcting with the tracking error of attitude angle, instead of only uses the attitude angle’s command. In addition, this method brings a rise in using information, increases the degree of freedom for designing control system, and obtains better performance than the normal method, such as the dynamic response characteristic and the stability precision of control system. The other one is a new quasi-terminal SMC method. This new method uses S-type function in designing nonlinear sliding surface, and can ensure that the output tracking errors converge to zero along the S-type trajectory in finite time. It not only ensures the terminal convergence, but also improves the performace of the whole process of dynamic response. If the parameters of control system are chosen suitably to ensure that the sliding function is approximated to zero, the approach motion phase of SMC can be almost eliminated and the robustness of control system can be improved markably.A hierarchy-structured predictive control(HSPC) method is proposed to improve the quickness and robustness of control system of HCV. This method divides dynamic motion model into two parts, and the control system is divided into two subsystems, too. So the relative degree of either subsystem is decreased, and the dynamic response becomes faster. In addition, the two subsystems are both designed by closed-form optimal generable predictive control(GPC) method, which consumes less time in calculation than normal GPC and is suitable for HCV. To improve the robustness of predictive control system, a feedback correcting algorithm is proposed. The algorithm is robust to the influence of strong nonlinear, outside interference and parametric uncertainties.To improve the performance of guidance-control system, several integrated guidance and control design principles are proposed according to the influences between guidance loop and attitude control loop. On one hand, in order to improve the performance of attitude control loop, the range and velocity of guidance commands, such as angle of attack, sideslip and bank angle, should be both limited. On the other hand, in order to improve the performace of guidance loop, the control gains of attitude control loop should be limited, or the influence of deflection angles should be ignored in guidance loop.The Six-Do F simulations of guidance-control system in different flight phases, such as climb phase, cruise phase and dive phase, demonstrate that the proposed control methods are all robust with respect to interference and parametric uncertainties, and can track the commands of attitude angles accurately. Research shows that the two new SMC methods and HSPC method proposed in this thesis have good performance in solving control problems for system, which is fast-variability, strong coupling, highly nonlinear and includes uncertain parameters. These methods are all feasible for HCV. This thesis can provide some references for the attitude control of HCV.