| Agricultural condition monitoring is a kind of monitoring on conditions including illumination, plant diseases and insect pests and plant density for growing crops, which can effectuate the growth of high quality and safety of crops. UAV plays an important role in agricultural condition monitoring which depends on its advantages including high wo rk efficiency, popular price, easy operation and universal applicability. With the pusuit of the UAV’s economical efficiency, people pay attention to reduce the cost. Compare to the setting of the sensor before, choosing cheaper sensor settings can not only lighten the load of the control system and lessen the cost, but also can improve the operation through the control strategy and guarantee the normal work of the system when a sensor failure happened in the running; if we use only a cheap sensor, it’s hard to meet the needs of UAV autonomous flight, and the measurement accuracy of the cheap sensor will be reduced too. In conclusion, combined measurement technique and information fusion technique are playing a critical role in the field of UAV system. The a pplications of these two technologies to UAV control system, which makes the valid data of multi-sensor complement each other possibly, provides more accurate, more comprehensive and much more stable data, will ensure the task of UAV safely and steadily.In this thesis, according to characteristics of the agricultural fixed-wing UAV which flies at a low speed and a low altitude, on the foundation of research and analysis about sensor features and fusion algorithm, we make a precision calculating and a desig n study on the attitude of the UAV. Firstly, under the premise of the function indexes in UAV control system, without changing the basic structure of the system and increasing the hardware of system, we proposed the overall design of the data fusion. Secondly, we put a research and analysis on characteristics and applicable scope of commonly used sensors on UAV, analyzed the measuring principle of the posture information sensor, sources and reasons of the error emphatically, and then put forward a preliminary mathematical model of the earth gravity field and magnetic field. Thirdly,we expounded the fusion algorithm of Kalman filtering and proposed that solving nonlinear system state equation and measurement equation with the extended Kalman filtering, and t hen we put forward two kind of allocation plans: first, the sensors configurations of combined accelerometer and gyroscope; sencond, the low cost sensors configurations combined with accelerometer, gyroscope, magnetometer and GPS, and then we used the eular angles method and quteration method to calculate the UAV attitude. Finally, we implement C language to achieve the design of fusion algorithm, and simulate sensors configuration on the MATLAB platform. The results prove that low-cost multi-sensor configuration scheme on the measuring accuracy and real-time performance can satisfy the needs of the system, contrasting with the accelerometer and gyroscope configuration scheme on course Angle measurement accuracy is greatly improved.In the validation process of the material object, we designed the hardware platform of attitude measuring system, and introduced the designed attitude measurement technology into the UAV control system, verified the solution through the UAV autonomous flight.We chose Northeast Agricultural University in Harbin ice rink side empty spaces as our experiment field, after the path planning, the data transmission module transferred back the flight data.With the collection and analysis of experimental data, experiment results prove that this kind of attitude measurement system can meet the sensor measurement accuracy and real-time requirement of the agricultural UAV control system, which achieve the goal of design, improve the reliability of agricultural UAV control system and provide a reference to the practical engineering application of agricultural UAV. |
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