Design And Implementation Of Four-rotor Aircraft’s Control System Based On Cortex-M4

Four-rotor aircraft has been more and more applications because of its simple structure, high flexibility and the advantages of vertical take-off and landing. Flight control system as the core of the flight platform, its performance has a direct effect on the entire flight. In this paper, design a flight control system suitable for four-rotor aircraft, the main contents are as follows:(1) In order to meet the requirements of autonomous flight of the aircraft, design the whole flight control system hardware. In the design process of the hardware, using the modular design concept, the whole flight control system is divided into the main control module, attitude and heading reference module, GPS module, status display module and power module, then gives details of the design process.(2) In the software design of the whole system, taking into account the main control module need to process the multitask, embedded uC/OS Ⅱ real-time operating system in the main chip of the main control module. In this paper, giving a detailed step of porting uC/OS Ⅱ to Cortex-M4 kernel, and plan the tasks that need to be managed. Other parts of the program using the common system, in the paper also gives a detailed execution process.(3)The precision of attitude angle will directly affect the attitude control results, and attitude controller as the foundation of the entire controller structure, but also affect the overall flight performance of the aircraft. To improve the accuracy of estimating attitude angle, the paper design the attitude angle algorithm based on Extended Kalman. In this algorithm, the dynamic acceleration was added into the observation equation as the noise and the offset error of gyro was added into the status equation to jointly calculate the attitude angle information. Finally, the algorithm is embedded into Attitude and Heading Reference module, comparing the algorithm output data with commercial sensor, the results show that the precision of attitude angle algorithm achieve the desired effect.(4) In order to test the performance of the system’s hardware and software, the attitude PID controller is designed, and the controller is embedded into the system, finally through the flight experiments to test the performance of the flight control system.The flight data and experimental results show that the hardware design of the flight control system meets the requirements, the software design architecture is reasonable, the Attitude and Heading Reference module can meet the accuracy demand of the flight, and the flight control system has reached the requirements.