Research On Unsteady Aerodynamic Modeling, Control Law Design And Clearance For Advanced Aerospace Vehicle

The aerodynamics/movement/control coupling problems in design of advanced flight vehicle, such as the 4th-generation flighter and the next-generation UCAV, are studied in this paper. New modeling, design and analysis methods based on multi-discipline research and application are developed and established.Unsteady aerodynamic modeling method in high angle of attack and its impact on flight dynamic system are researched in the first part of the paper. To solve the aerodynamics/movement coupling problem in high angle of attck when the 4th-generation fighters perform post-stall maneuvers, based on the dynamic modeling thoughts, ordinary differentical equations are used to describe and reveal the unsteady aerodynamic characteristics. A new method is introduced to improve the identification procedures based on wind-tunnel experiments: Linear Regression method is used to identify the linear parameters such as characteristic time constant with small-amplitude forced oscillation experiments; Genetic Algorithm method is used to identify other nonlinear parameters with large-amplitude forced oscillation experiments. Taking delta wing model with center body as the example, this modeling method is tested and verified. The results show that the established models could predict the unsteady aerodynamic forces accurately in arbitrary movement and is easy to coordinate with flight dynamic equations, which shows the feasibility in aeronautic engineering. Furthermore, using Modal Analysis method, the impacts of unsteady aerodyanmics on flight dynamic system are studied and the primary flight control law for high angle of attack is designed with Eigenvalue Assignment method. Comparative analysis is carried on different unsteady aerodynamic models, and the results reveal the potentially problems if the flight control law is established based on traditional aerodynamic derivative models.The flight control law reconfiguration design and the closed-loop flight dynamic characteristics for the advanced flight vehicle in fly-wing configuration are studied in the the second part of the paper. Firstly, the flight control law reconfiguration design in the case of side-slip sensor failure is studied for fly-wing aircraft, which is static directional unstable and uses multi-surfaces to prvide directional control. Taking a small-scaled UCAV model as the example, different methods, such as Attainble Moment Set, Attainable Equilibrium Set, are used to analyse its aerodynamics, control efficiencies and the open-loop flight dynamic characters. The multi-objective optimization method considering flight qualities, control power and robustness is introduced to design the lateral-directional flight control law. And the entire control law consists of dynamic-pressure scheduling, lateral-directional coupling control, AOA limiter and control power allocation. Moreover, the flight control law clearance frame based on computational flight dynamics is established to verify the validity of flight control law. Based on Monte Carlo shooting method and AES method, the linear impacts such as aerodynamic uncertainty are analysed and evaluated; based on Bifurcation Analysis method and Regions of Attractions analysis method, the nonlinear impacts, such as the dead-zone/saturation/rate saturation of actuators, are estimated. And then, flight simulations are used to train the operator and evaluate the atmosphere turbulence impacts. The research and test flights'results indicate that the flight control law using only roll/yaw rate feedbacks could help to stabilize the aircraft when the side-slip sensor fails, which guarantees the flight safety.The new methods established in this paper for aerodynamic modeling, flight dynamic analysis, control law design and clearance have rich engineering referece value in the design and analysis work for developing the next-generation advanced flight vehicle.