| The quad-rotor aircraft is an electric multi-rotor autonomous vehicle which is VTOL and can be remote controlled. It is a non-coaxial disc aircraft in the overall layout of forms. Compared with conventional rotary wing aircraft, its special mechanical structure and flight dynamics characteristics are of great significance in the scientific and technological research and application. Taking the quad-rotor aircraft as the object, this thesis mainly discusses the following two questions:dynamic modeling of the six degrees of freedom of the quad-rotor aircraft, and based on this modeling, achieving the nonlinear control method of under-actuated systems.The main contents of this thesis include the following aspects:First of all, according to the body composition and the movement mechanism of the quad-rotor aircraft of six degrees of freedom, this thesis establishes the airframe and the ground coordinate system describing the flight movements of the quad-rotor aircraft, and gives the coordinate transformation matrix between the two coordinate systems. Based on the dynamical system model of the quad-rotor aircraft and the aerodynamic knowledge, this thesis then deduces full state nonlinear dynamic equations of the six degrees of freedom of the quad-rotor aircraft by the Newton-Euler theorem. Finally, on the basis of system mathematical model, this thesis appropriately simplifies the system model, ignoring the elastic deformation, air turbulence and other external interferences.Secondly, based on the previous simplified model, this thesis analyzes the under-actuated characteristics of the quad-rotor aircraft, whereby this thesis proposes a dual control loop and some under-actuated control strategies of the six subsystems. According to the chosen system state variables and control inputs, this thesis then obtains the system equations which meet the strict feedback form, and on the basis of which, designs a Backstepping-based flight controller of the quad-rotor aircraft. This controller is able to track every posture calm, designated reach, position and yaw angle trajectory with no steady-state error. Finally, the algorithm validity is tested through simulation experiments.Thirdly, in order to resolve the problems of the impact of the system model error and the sensitiveness of the quad-rotor aircraft to external disturbances, the system model error estimator and the error integral are introduced. At the same time, Backstepping approach is applied to establish the system adaptive controller to finally achieve the adaptive control of the quad-rotor aircraft. This adaptive controller shows more excellent performance in the case of sensor interference, external disturbance and so on. Finally, the effect of the controller is tested through simulation experiments.At last, the thesis presents the summary of this study and the outlook of the future work. |
