Nonlinear Controller Design For Hypersonic Vehicles Considering Flexible States

Modern war demands rapid response time to systems, and hypersonic vehicles can reduce response time effectively, so it is the main developing direction either for attacker or defender. The dynamic characteristics of the hypersonic aircrafts will vary considerably over the flight envelop than other aircrafts due to their extremely wide range of operating conditions. Furthermore, because of airframe-integrated scramjet utilized and the flight conditions of high altitudes and Mach numbers, hypersonic aircrafts are very sensitive to changes in atmospheric conditions. Moreover, many aerodynamic and propulsion characteristics still remain uncertain and are hard to predict due to the effect of the structural dynamics, propulsion aerodynamics and coupling between them. As a result, the hypersonic vehicle model is uncertain, multivariable, unstable, and possesses significant input-output cross-coupling. Therefore, it is essential to design flight controllers with high non-linear control ability and robustness for hypersonic aircrafts.In order to grasp complex dynamic characteristics of the hypeisonic vehcle models, feature and impact of hypersonic speed flow and hypersonic vehicles body/ engine integrated structure are researched firstly. Then, the modeling of hypersonic and analyzing of its aerodynamic characteristics is carried out. The model’s differential equations contain rigid and elastic modes. By analyzing the results obtained above, the dynamic characteristics and flight specialty of hypersonic vehicle can be understood, and it is possible to provide appropriate objects to design flight control systems for hypersonic vehicles.In order to solve the strong nonlinearity and coupling of model of hypersonic vehicles, the theory of feedback linearization is introduced to convert the accutate nonlinear mathematic model into the equivalent linear model to design te control method. Through proper transformation, dynamic inversion flight system for hypersonia is obtained to stabilize the system and relieve the coupling effects. For the mismatching uncertain controlling problem of the hypersonic vehicles, adaptive back-stepping is applied to design robust controller for the mismatching uncertain longitudinal model of the vehicleto guarantee the global stability and restrain the disturbance it brings. Simulations prove the efficiency of the proposed method. The boundedness the work to be done are analyzed.