Research On Nonlinear Flight Control Law Design Of Aircraft With Vectoring Thrust

The application of thrust vectoring control technology makes the aircraft possess the ability to fly in post-stall domain, therefore the flight envelope is extended. The thrust vectoring control technology and post-stall maneuverability enhance the aircraft's combat effectiveness greatly, and cause the worldwide interest. In this dissertation, an exploring study on flight control law design of the aircraft with thrust vectoring is completed. The main contents are summarized as follows:1. The application background of thrust vectoring technology on aircraft and its advantages are analyzed. The main characteristics of some type of vectoring nozzles are discussed, the expression of thrust vectoring force and moment are set up. Then, the nonlinear motion equations of aircraft with three axes of thrust vectoring are deduced.2. For general nonlinear system, a control law design method which integrated the nonlinear dynamic inverse theory, adaptive fuzzy system and slide model control is developed. A stable adaptive law is determined by using the Lyapunov theory, and the boundedness of all signals as well as the convergence of the tracking errors of the closed-loop system is guaranteed. This method set up a link between fuzzy system and adaptive control theory, realized the unification of adaptive control and robust control. Using this method, the flight control law which suits to the vectored aircraft flight in post-stall domain is designed in this paper.3. The aerodynamic characteristics and mechanism of flight dynamics under the condition of post-stall maneuvers are discussed, and then the inputs of adaptive fuzzy system are determined. Using the control law and nonlinear motion equations built above, some typical post-stall maneuvers are simulated and the effects of thrust vectoring on post-stall maneuver are analyzed. The results show that the control law can control vectored aircraft to accomplish post-stall maneuvers very well and it is very robust to model uncertainty.4. The application of control law developed above to the problem of reconflgurable flight control is described. Based on the simulation results, the effects of learning rate (or adaptation gain) and slide model terms on the control system arediscussed. Comparing with adaptive control, the control law is helpful to improve system's transition response and reduce undesirable oscillations, provides nearly perfect tracking in the case of undetected failure.5. The mechanism of two possible ways of thrust vectoring control: force and moment control are analyzed. The effects of thrust vectoring on aircraft supersonic performance, take-off and landing performance, low speed and high angle of attack performance are studied. The air combat effectiveness of thrust vectoring control and post-stall maneuvers are also analyzed.