Resrarch On Maneuver Flight Control Technology For Static Unstable Flying-wing Unmanned Aerial Vehichle

The static unstable fly-wing unmanned aerial vehicle(UAV) has great strategy, tatics value and board prospect of application in military field because of its advanced aerodynamic configuration and outstanding stealth and maneuver capabilities. The thesis proposes a maneuver flight controller design method for such high performance UAV platform. The controller can make the UAV preform longitudinal and latitudinal maneuver motions excellently in the presence of several kinds of internal uncertainties and outer disturbance. As a result, the full flight potential of static unstable fly-wing UAV is reached, and the robustness as well as the adaptability of the flight control system can be improved.Firstly, the thesis discusses the development history and the current study situation of static unstable fly-wing UAV, and the advantages bring about by the maneuver flight. Then the kinematics and dynamics six freedom nonlinear modeling are built based on the aerodynamic features of the static unstable fly-wing UAV. Besides, the complicated nonlinear characteristic such as kinematic coupling and aerodynamic coupling and manipulation coupling are analyzed according to the mathematical model. The thesis also describes the additional affections to the coupling phenomenon caused by the static unstable feature and fly-wing configuration, so the maneuver ability of the sample UAV is given.Secondly, the thesis proposes the whole control structure and design scheme of closed-loop maneuver flight control system. Through the control structure analysis, the specific functions of the inner/outer loop controllers and control allocation, as well as the reliance and compensation relationship between the baseline and augmented controllers are defined in the flight control system. Then, the design methods for the longitude and latitude inner loop controller based on the combination of robust servomechanism nonlinear inverse control and robust model reference adaptive control are proposed. In the inner loop controller, the robust servomechanism nonlinear inverse control is used to counteract the nonlinear coupling items in the maneuver flight and to track the certain order reference command as well as suppress the corresponding disturbance. In the following, the closed-loop system with robust servomechanism nonlinear inverse control are considered as the ideal reference model, so that the robust model reference adaptive controller with any relative order is developed, which not only can compensate for the robust servomechanism nonlinear inverse control but also can blend the best of both control schemes. The commands tracking performance and the robustness of the inner loop baseline controller is proved.Next, the thesis gives the construction method and the design procedure of the inner loop augmented controller based on the H_∞optimal control. During the construction of the augmented controller, the uncertain items in the flight control system and the parameter estimation error in the adaptive control are treated as the disturbance part in the system, so the H_∞augmented controller which fulfills a proper performance index is proposed to eliminate the adverse effect to tracking errors bring about by the disturbance part. So the transient tracking response performance of the closed-loop control system is greatly improved. And the thesis also reveals that the amount of the transient performance improvement depends on the performance level of the H_∞augmented controller. The theoretical analysis has been made to prove that the adding of the H_∞augmented controller can not only greatly improve the transient performance but also will not destroy the ideal property of the inner loop baseline controller. After the design of the inner loop controller, the construction and the stability analysis of the outer loop robust adaptive controller are given.In the following, based on the analysis of the actuator physics limitation, the nonlinear property of the rudder effectiveness along with the flight states and the couplings between the manipulating surfaces in the control allocation, the thesis proposes a dynamic control allocation algorithm with varying weight matrix. The proposed control allocation algorithm has the direct and fast allocation property as the linear allocation, which ensures the real-time control allocation operation. In the algorithm, the actuators with better linearity have bigger allocation weights, which can reduce the allocation errors caused by the actuator nonlinearity. Through solving a quadratic regulation optimal problem, the balance between the allocation precision and the allocation step is kept.Finally, to show the effectiveness and rationality of the proposed maneuver flight controller, the numerical simulation platform is built based on a sample static unstable flying-wing unmanned aerial vehicle. Then the command tracking performance, robustness and the transient performance of the closed-loop control system are validated through nonlinear simulation. Particularly, several typical maneuver flight simulations such as longitude fast climb and dive maneuver, latitude fast and continuous turning maneuver and comprehensive ‘Retournment’ maneuver are made to reveal that the designed maneuver flight controller is able to perform the desired maneuver behaviors stably, accurately and quickly, regardless of the internal uncertainty and outer disturbance in the closed-loop control system.