The Design Of The Quad-rotor UAV Control System Based On The Cascade PID Control Algorithm

With the continuous development of microelectronics technology in recent years,quadrotor UAV achieved rapid development,and it has been widely applied in aerial photography,remote sensing, disaster relief, public security, fire, terrorism, cinematography, environmental monitoring, express delivery and other related areas due to its advantages including flexible control,low cost,etc.Since the quad-rotor UAV is a typical non-linear, strong coupling, underactuated and multiinput multi-output complex system, so that four-rotor UAV control system becomes difficulty UAV research.The study is to design a complete set of quad-rotor UAV Control System which adopts cascade PID control system error correction algorithm. The whole control system is divided into the following four steps: First, the design of four-rotor UAV control system hardware system. Hardware control system is STM32F407VGT6 as the master controller. Remote command and the motor speed control respectively adopt PWM input capture and PWM output function of the internal timer in the master controller, inertial measurement components MPU6050 and magnetoresistive sensor AK8975 respectively measure the aircraft angular velocity, acceleration and reluctance value,and the wireless communication module is used in comunication between control panel and upper computer. Second, IIC communication between master controller attitude measurement sensor. The master controller apply the sliding mean filter and Newton interpolation smoothing processing of raw sensor data after reading the posture sensor data, the complementary filter fuse the data of gyroscopes, accelerometers, magnetometers complementary. At last, calculate the UAV space attitude angle by quaternion method. Third,build the model of four-rotor UAV control system nonlinear dynamics based on Newton’s second law and torque balance principle,using LPV treatment linearize the nonlinear system to obtain the transfer function of each channel of UAV, build the simulation model of Cascade PID in MATLAB / Simulink, and verify the rapidity stability and accuracy of cascade PID control algorithms control systems by the pitch angle, roll angle, yaw angle and Z-axis direction simulation and the interference simulation to these four channels. Fourth, elaborate the implementation of the cascade PID control algorithm. Write the control system program in C language, compile the software and download it to the control board then debug the PID parameters and test the flight. Test results manifest that this designed control system is able to match with the other body modules well and realize accurate and stable fly control, which achieve the expected design goal.