Research On Attitude Calculation And Control Algorithms Of Small UAV Based On Strap-down Inertial Navigation System

In recent years,the small unmanned aerial vehicles(UAV)are widely used in the field of military,technology and civilian because of its advantages of small-size,low-cost,highmobility and high-security.The flight control system is a key part of the small UAV,whose performance directly determines the stability of small UAV and anti-jamming capability.As the core of flight control system,attitude calculation and control algorithms have become the important research content.In this thesis,taking the four-rotor small UAV as the research object,we focus on the attitude calculation and control algorithms in flight control system.Firstly,the background and significance of the research are clarified,and the development of small UAV,attitude calculation algorithm and control algorithm are briefly summarized.Then,we introduce the strap-down inertial navigation system and its working principle and the basic principle of flight control.The main works are as follows:1.Several attitude calculation algorithms based on SINS,the working principle of inertial sensor and the algorithm of sensor data fusion are studied.Considering the shortcomings of the complementary filter parameters and the characteristics of Kalman filter,we propose an improved complementary attitude analysis algorithm based on quaternion.With the characteristics of adaptive,the algorithm can automatically adjust the size of the sensor confidence factor according to the speed of the UAV attitude.The simulation results show that the accuracy of the attitude angle is improved to a certain extent.2.Several attitude control algorithms for four-rotor are introduced.And we study the basic principle and the method of parameter setting of classical PID controller.Based on the characteristics of high-flexibility and high requirement for stability of small quadrotor,combined with the theoretical analysis,two kinds of higher-attitude-stability programs are designed on the basis of classical PID controller.We mainly study and simulate the attitudestabilization scheme of the angle/angle speed cascade PID controller.3.Based on the idea of modularization,we design the hardware and software systems of the small quadrotor.After analyzing the device selection,design idea and circuit schematic,the flight control hardware system based on STM32F103 is designed.Then we develop the software system in the Keil MDK.Finally,we complete the fight test using the small quadrotor,and the results show that the attitude calculation algorithm proposed in the thesis can be used to calculate the angle of small UAV with high precision,and the angle/angle speed cascade PID controller shows higher stability.