Advanced Uav Control Strategy

The design and implementation of nonlinear flight control system is a key technology in the research of advanced U AV. A systematic study on robust stability analysis, robust tracking control, and full envelope gain scheduled controller synthesis has been performed In this dissertation. The main results and contributions are described as follows: (1) Feedback stabilization methods of non ?minimum phase systems have been investigated. An algorithm that converts non ?minimum phase systems to minimum phase systems by output redefinition is proposed. Stabilization approaches are presented by decomposing the system into two parts: a minimum phase part and a non梞inimum phase part. The sufficient conditions of stability robustness are derived for feedback stabilizing systems with its input unmodelled dynamics satisfying local 155 (los) or small 梥ignal L 2 stability. (2) Based on integral control and sliding mode control, a robust universal regulating law is synthesized. The only precise knowledge about plant in design Is the relative degree and the sign of high 梖requency gain. For systems that have the same knowledge, the universal regulating law can be used. This is very useful in the condition where uncertainty Is a little large; what s more, for relative degree one systems and relative degree two systems, the regulators are the classical P1 controller and PLD controller followed by saturation. Its robust control frame is simple, and the designing idea Is very close to that in project. So, the method is very practical. Robust control of a modeling error compensation approach is proposed for nonlinear systems whose estimate functions are known. The model error is viewed as an extra state that is estimated by applying high ?gain observer, which gives the control system some degree of adaptability. The implementation method in application is also investigated. (3) A series of problems in flight application of full envelope gain ?scheduled controller, such as effective implementation, global stabilization, and selection of scheduling variable, are solved. The linear properties that must be preserved in the implementation of nonlinear gain ?scheduled controller are presented. A new 桰I? implementation frame for tracking control is addressed, in which the trimming value of systems is not introduced, and its control gain can be easily got from linear controller. The sufficient conditions needed for global stability and robustness in scheduling control gain is proposed. Based on flight dynamics, the basic principle is given that the scheduling variable in trajectory tracking should be. selected as a function of inertial velocity, flight 梡ath angle, and desired yaw rate. The implementation frame and the principle have all been applied in some kind UAV s terminal phase flight control of angular ?velocity tracking. The flight results show good full envelope tracking properties. (4) Robustness analysis methods in flight control systems are discussed. A robustness analysis model of trajectory tracking for nonlinear systems is built, and the robustness analysis of trajectory tracking is equivalent to the optimal problem with constraints. It enables the complex problem easy to be analyzed and solved. Combining the Bode mismatch envelope with ~i analysis method, an algorithm for analysis of flying qualities robustness is addressed. The flight ?determined stability analysis method is presented, and it is a...