The Research And Design Of Sensor System On Multi-Rotor UAV

In recent years, Multi-Rotor UAV has been widely applied to many fields, such as aerial, public security, agriculture, electric power and other industries due to the advantages of its small size,low cost and convenience in use and so on. However,in practical applications, there are still some problems such as large error of attitude angle estimation, unstable altitude data, and poor altitude control effect in sensor system of Multi-Rotor UAV . To solve the problems above, this paper do some research and improvement about the UAV sensor system as follows:(1) According to the practical application, the hardware structure of the Multi-Rotor UAV sensor system is designed in this paper, including the IMU module,the geomagnetic module and the GPS module. The IMU module is used to estimate the attitude angle and the altitude of the UAV, which is mainly composed of MEMS accelerometer, gyroscope and digital barometer. The geomagnetic module is used to obtain geomagnetic field intensity. The GPS module uses the RTK system with high precision, which is used to obtain the altitude and velocity of the UAV.(2) On the basis of the hardware of the sensor system designed above, this paper designs the embedded software of the IMU module and the geomagnetic module. To improve the real-time performance of the IMU module,the FreeRTOS is embedded into it. In addition,the data receiving program of GPS module is also designed.(3) The accelerometer data contains dynamic acceleration during the actual flight, resulting in large errors in attitude angle estimation. This paper considers importing the dynamic acceleration as noise term into the observation equation, and then ,uses the extended Kalman attitude estimation algorithm to get accurate attitude angle. Furthermore, the optimized algorithm is compared with the complementary filter algorithm and the algorithm of commercial sensor-Ellipse-N separately.(4) In view of the inaccuracy and drift of altitude value, resulting in the poor effect of altitude control,this paper use the control method called MRSMC to realize the precise control of UAV height with the altitude and velocity information provided by RTK system,and verifies the improvement effect through actual flight test.