Research On Control System Of Four Rotor Unmanned Aerial Vehicle

Four rotor aircraft is a kind of multi-rotor aircraft,the rotors are directed upwards and they are placed in a square formation with equal distance from the center of mass of the four rotor aircraft.The four rotor is controlled by adjusting the angular velocities of the rotors which are spun by electric motors to control the attitude and position,it is because of this simple structural design that it has flexible mobility and it can vertically hover and flight along arbitrary direction,its unique structure and motion control methods which can be applied to a variety of complex environment.However,since the aircraft has six degrees of freedom(three translations and three rotations),there are only four inputs,so it is a four inputs,six outputs multivariable under-actuated system.At the same time,the attitude motion and the position motion are coupled with each other,so that the kinematics model is highly nonlinear.In order to ensure the safety of aircraft,fast and stable flight that the attitude and position control is the core problem of the whole vehicle control.By combining the feedback information of the control command with the attitude measurement system,the PWM signal of the control actuator is solved by the control system to drive the motor and the propeller to achieve reliable flight action.According to the characteristics of model four rotor aircraft,this paper takes the small four rotor aircraft as the research object,based on the Newton Euler equation,the kinematics and dynamics model of the four rotor aircraft is established,and the underactuated control problem of the aircraft is solved by decoupling the system model of the aircraft.By simplifying the system model,the PID control algorithm and the linear quadratic(LQR)control algorithm are designed respectively,at the same time,a cascade PID control algorithm is designed to control the position of the aircraft.According to the designed control algorithm,the simulation environment of four rotorcraft is built by using MATLAB/SIMULINK tool.The simulation results are optimized by simulation,and the simulation results are obtained by optimizing the parameters of the model and the simulation parameters of the controller,finally,the simulation results of attitude and position control and fixed point control for the four rotor aircraft are obtained.The simulation results verify the correctness of the algorithm,and realize the accurate control of the attitude and position.In order to verify the effect of PID control algorithm in real environment,the design based on STM32F4 controller,the real-time control of the aircraft is carried out with the combination of gyroscope and accelerometer sensor MPU6050,magnetometer AK8975 and barometer MS5611 MEMS sensor measurement system.According to the characteristics of MEMS sensors,Using the FDATOOL of MATLAB,the fifteen order FIR low-pass filter is designed for the accelerometer and gyro output data respectively,a sixteen depth window sliding filter is designed for the magnetometer output data,the data of the gyroscope,accelerometer and magnetometer are filtered and fused by the complementary filter to complete the attitude calculation of the aerocraft.The C language is used to write the software control algorithm,and the experiment of the hardware and software flight system is carried out,the experimental results show that the designed control algorithm can achieve rapid,stable and accurate control of the aircraft,and the design of control algorithm has good robustness.