The Synthesis Of Intelligent Robust Flight Control Systems For UAVs

As great benefits are got from the applications of UAV (unmanned aerial vehicle), especially the applications in military field, more and more attention is paid to the development of UAV in the world. To accomplish the complicated missions safely and effectively, there must be an advanced flight control system for UAV. To reduce the effects of the uncertainties and disturbances on flight performances for minimal UAV, classical control methods have been replaced with other advanced control methods gradually.Robust design process requires both a nominal model and some characterization of the model uncertainties, so it is difficult to get a favorable performance because of the conservative designs in system controllers. Neural networks can be used in the control problem for nonlinear, uncertainty system.The intelligent robust controller, which deals with uncertainty and disturbance, is studied here; some fruitful results are presented as follows:1. The UAV's nonlinear differential equations, which is consisted by a six degree of freedom (6-DOF) model, is built and linearized. In order to design a controller which stabilizes the feedback system, the open-loop characteristics of the aircraft model is analyzed in this section.2. The description method and classification of uncertainties are proposed. And then this dissertation survey the technique of transforming the problem of flight control to standard H∞ control. The output feedback using H∞ control theory was presented to design controller by choosing weight function matrixes. Simulation results indicate that the robust controller can improve the control performance effectively according to the classical control methods.3. Using the neural network's ability to approach the nonlinear model, a new way to augmentation of an existing robust controller is introduced. Simulation results show that this method can solve the small UAV's control problem in the condition of winds.4. This dissertation introduces a simple heading tracking method for the lateral control system. The affection of control parameters is surveyed and evaluated.