Four-rotor Aircraft Attitude Angle Estimation And Control

Because of simple mechanical design, small volume, fast flight speed, strong mobility, flexible control and so on, four rotor aircraft has been widely used in the field of military, civil, and scientific research. At the same time, it is also a complicated nonlinear and under actuated system. It is difficult to establish an accurate mathematical model to describe its attitude.Based on the working principle and characteristics of the accelerometer, magnetometer and gyroscope, a calculation process of attitude angle is given in detail about four rotor aircraft in flight state. Thesis focuses on the analysis of the different data fusion algorithms about the attitude angle data fusion problems. use the angles after fusion to achieve a stable control of small angle perturbations of the four-rotor aircraft. Use the accelerometer, the magnetometer and coordinate transformation to establish a mathematical model to describe the attitude angles, at the same time, use the gyroscope to establish another mathematical model to describe the attitude angles. Constructing math model and calculating the compensation coefficient by the least squares method is in order to compensate the environment error which has most effect on the precision. After the error compensation, the yaw angle can be estimated accurately. Use the method of minimum variance estimation to calculate the weights, then a data fusion model about the attitude of four-rotor aircraft is established. Using the standard Kalman Filter and extended Kalman Filter for data fusion, successively. By analyzing the calculating model of the attitude angles, the state equation and measurement equation are established. They can correct gyro errors real-time. Simulation by MATLAB, weighted fusion algorithm is proposed to improve the accuracy of attitude angles. and modeling simple, small amount of calculation. The effect of the data fusion method based on Kalman Filter is much better than the weighted fusion method, but pitch angle and roll angle are estimated before the yaw angle, Real-time performance is poor. To Extended Kalman Filter, modeling process and the calculation process are complicated, But its effect is optimal. Finally fusion estimation angle and target angle difference as input, PID control algorithm is used to get the adjustment quantity of the motor, to make the aircraft balance within a small Angle.Based on the Android platform, the four rotor aircraft ground station is designed to complete the system test. The experiment results show that the fusion attitude angles using the Extended Kalman Filter can realize the control of four-rotor aircraft in a small Angle disturbance, and provides a reference for further expansion and development of four-rotor aircraft.