Uav Formation Flight Control System Design Methods And Applied Research

This dissertation mainly investigated the design and application of autonomous formation flight control system of unmanned aerial vehicles (UAVs). First, the models of the autonomous formation flight control system of UAVs are considered. Basing on the motion equations of UAV and formation's plane geometry, the model of space formation flight system is established. Second, the aerodynamic coupling effects in formation flight are addressed. Third, autonomous formation flight control methods are studies, such as fuzzy logic control, adaptive control and sliding mode control. The formation flight adaptive control system and sliding mode control system are designed under considering of uncertainty in formation flight respectively. All the chapters of the dissertation include simulation analysis. The main works of this dissertation are as follows:1. Establishment of formation flight system model. The relative motion equations between two adjacent UAVs in formation are established in the ith UAV's plane wind frame. And the space model which includes the motion of single UAV and relative between two adjacent UAVs in formation is established in the ith UAV's wind frame.2. The aerodynamic coupling effects in formation flight are addressed. In chapter 3, these aerodynamic coupling effects are properly modeled use horseshoe vortex model in formation. The induced velocity and aerodynamic forces which are introduced by the i-lth UAV of formation in the ith UAV are calculated. The autopilot in the ith UAV is modified by adding the aerodynamic coupling effects. After comparing simulation results of two kinds of systems, we can find that the responses of the new system which includes these aerodynamic coupling effects are larger than the system which does not include them.3. Application of fuzzy logic control in formation control system is considered. In the background of air refueling mission, the model of the lead-wing formation flight fuzzy control system is established. This system is based on the control of wing's velocity, altitude and heading angle to realize formation flight. The simulation results show that this system can yield satisfactory performance in formation flight. The method of fuzzy logic control is feasible in formation flight.4. The formation flight system always includes uncertainties, adaptive control systems of formation flight are designed to deal with these uncertainties. The uncertainties may come from internal formation flight system or external circumstance. This dissertation discussed adaptive control method using plane relative motion equations and modified autopilot in the ith UAV under two kinds of cases: unknown aerodynamic coupling parameters of internal formation flight system and unknown model of formation flight system. While the formation flight system model is partial unknown, the unknown part of the model is hardly to express. So in this case, we designed adaptive controllers by considering the unknown part as time-variation function and constant function respectively. From simulation results, we found that the time of the formation flight system getting steady with partial unknown model is longer than that with unknown aerodynamic coupling parameters.5. The formation flight sliding mode control system is designed using the nonlinear space formation flight system model. The system can control the ith UAV under the condition of communication with the adjacent UAV in formation. Due to the unknown of the upper bound of the uncertainty in formation flight system, this dissertation also design the adaptive law to estimate the unknown bound. Several simulation results show that the formation flight sliding mode control system with uncertainty can yield satisfactory performance. And the space formation flight system model is fit for analysis while lead aircraft maneuvers.This dissertation investigates the control methods of formation flight system of UAVs with the uncertainties. By discussion systematically and simulation results, several concludes which show the characteristics of application of these control methods in formation flight system are presented.