Design On The Control System Of Quad-Rotor UAV With Actuator Saturation

Quad-rotor UAV has a wide range of uses, low cost, cost-effective, good maneuvering performance, convenient use. In the modern war it plays a important role,in the civilian fields is also important. Quad-rotor UAV technology has developed rapidly in recent years, and the control technology is also a hot research topic. PID control, LQR control, feedback linearization, backstepping and other control methods are emerging endlessly. Due to physical constraints and the need for security, almost all of the control systems are subject to actuator saturation constraints. Quad-rotor UAV is also the case, and the actuator saturation has an important impact on the overall stability of the control system. We design a control system of quad-rotor UAV with actuator saturation in this dissertation.In order to avoid binding force in the equation, the mathematical model of quad-rotor UAV is established by analytical mechanics method, which can overcome the difficulty of vector mechanics to a great extent. The model is a nonlinear mathematical model with six outputs and four inputs. The system is divided into four channels to control, respectively, is altitude direction, yaw, pitch and roll direction. For the direction of altitude and yaw, the control law of PD is used to control the system.As a result of the pitch channel and roll channel have typical characteristics with multiple integrator, so for pitch and roll direction. In this paper, we design nested saturation control method to control.Firstly, the nested saturation linearization control method is designed. After transforming the original nonlinear system into a linear one, the method can be used to stabilize the linearized system, but not the orignal nonlinear system. In the process of designing the control law, there is no limit to the saturation of the system, we can choose free parameters, which can improve the dynamic performance of the system.The simulation results show that the original nonlinear system has better dynamic response under the control law.Then, considering the shortcoming of linearization method, can only be guaranteed in the initial value is relatively small for the original nonlinear system has abetter control effect. Thus, this paper proposes the nested saturation nonlinear control method, this method can global stabilization of the original nonlinear system. In the process of designing the control law, there is no limit to the saturation of the system,we can choose free parameters, which can improve the dynamic performance of the system. Simulation results show that the nested saturation nonlinear control law can make the original nonlinear system converge quickly, and the overshoot is small.In summary, the nested saturation control method for the quad-rotor UAV with actuator saturation has the advantages of overshoot small, fast convergence and excellent control performance.