Flight Control System Design Of Multi-rotor Aircraft Facing Autonomous Cruise

Due to its simple structure and flexibility, multi-rotor aircraft is extremely popular with business organizations and research institutions, and it has great prospects in both civil and military fields. In recent years, with the proposal of the path planning and autonomous navigation of multi-rotor aircraft, the navigation algorithm and control algorithm of flight control system plays a more and more important role. So this thesis regards quadrotor as the research object and does the following research works according to the existing experimental conditions.Firstly, a set of flight control system is designed based on research content and practical requirements. In order to verify the rationality of the navigation algorithm and control algorithm, a hardware platform based on ARM embedded chips and Inertial Measurement Unit(IMU) is designed. A feasible and effective software architecture is also designed to implement the complex algorithm and flight mission. Then the basic architecture of the flight control system is completed.Secondly, the low-cost attitude sensors, used in this thesis, have been calibrated. Due to the limitation of experimental conditions, attitude sensors are calibrated at the greatest extent based on the error model. In order to realize autonomous cruise, this thesis designs an integrated navigation system based on extended Kalman filtering algorithm, establishes state equations and observation equations from the data of altitude sensors and GPS, and estimates the optimal navigation information. Finally, the integrated navigation algorithm is verified by comparing the effectiveness of the algorithm in the indoor and outdoor experiment.Then this thesis proposes the design of the control algorithm. By analyzing the principles and characteristics of the aircraft, the flight control algorithm is divided into three parts:attitude angle control, height control and position control. This paper does a certain degree of improvement for three control circuit based on the classic PID control algorithm. The control of attitude angle is turned into the cascade PID control, which improves the stability of the control system. The vertical speed of geographic coordinates is used to replace the differential link in height control, which improves the anti-interference ability of control system. The position control omits the differential link of location circuit, then shifts control output directly to the attitude angle control loop, which reduces calculated quantities in same control effect.Finally the flight control system is assembled with a small quadrotor with 450 mm wheelbase, by which the above three control circuits is tested. This quadrotor implements the autonomous navigation finally by analyzing of the data transmitted to the PC during the flight, observing the actual flight state of the quadrotor and regulating the control parameters. All these tests verify the stability of this flight control system and the rationality of the navigation algorithm and the control algorithm.