Research On Longitudinal Stability Augmentation System Using Active Control Technique For Flying Wing Unmanned Combat Aerial Vehicle

Flying Wing Unmanned Combat Aerial Vehicle (UCAV) adopts special aerodynamic configuration, for its superior performance, it will be one of the most important tactical forces in the future battlefield. For the purpose of improving maneuverability, relaxed longitudinal static stability is studied based on a certain Flying wing UCAV in this paper.Firstly, the motion of the UCAV is expressed in twelfth-order differential equations which are six degrees of freedom rigid-body motion, thus, a mathematic model of relaxed longitudinal static stability UCAV is built. Then, the concepts of Active Control Technique (ACT) and longitudinal static stability are introduced, the effects of relaxed longitudinal static stability on longitudinal aerodynamic parameters of UCAV are also expatiated. Three compensative methods are presented based on the analysis of longitudinal dynamic characteristics of UCAV in this paper. In order to ensure the robust stability of flight control system, flight envelope is divided into several areas.Classic control theory, optimum control theory and linear matrix inequality (LMI) theory are used into the design of flight control system. In this paper, the theories of Linear Quadratic Regulator (LQR) and Linear Quadratic Tracker (LQT) with corresponding searching optimization algorithms are detailed, thus, good effect are obtained by applying those theories. Then, linear matrix inequality theory is discussed. Combining linear quadratic with regional pole assignment, the robust stability of flight control system is ensured, further more, multi-objective optimization is achieved during the process of design.Finally, based on the linear matrix inequality theory, the flight control system of relaxed longitudinal static stability UCAV is presented. The simulation results in the full envelope verify the feasibility of our research.