The Research On Attitude Measurement And Control Of Satellite Antenna Based On MEMS And Electronic Compass

Marine satellite antenna system is a high-tech product, which provides the basic leisure andentertainment solution for the people working in the maritime mobile platform, and it is animportant part of building a harmonious working and living environment. Different from thefixed receivers in land, the antenna is facing the impact caused by sea waves and the changes inthe direction of the hull sailing posture interference, so that the antenna attitude measurementand control becomes more difficult. Most products available in the market use angular ratesensor and GPS as attitude measurement methods, and most of products use the framework oftwo-axis to stabilize the direction of antenna. But GPS update data slowly and easily lostsatellite signal, and the two-axis frame can not completely solve the roll problem. In this thesis,considering the cost and accuracy requirements of stability system, MEMS sensors andelectronic compass are used to measurement the attitude of the antenna, and through theframework of three-axis movement to make up for roll angle changes.Firstly, this thesis outlines the background of marine satellite antenna research,development status and related technology infrastructure. After comparing several methods ofattitude determination, propose of combining MEMS-based sensors and electronic compass forattitude determination is made. Considering the difficulty of system implementation andstabilization affect, the use of closed-loop attitude stabilization method and add the auxiliaryfield strength to stabilize the direction of antenna. Then it focuses on the best estimate attitudeof the satellite antenna, and a tightly coupled Kalman filter algorithm is derived by usingattitude angle error equation, the accelerometer output equation and geomagnetic outputequation expressed in quaternion. For solving the problem of attitude estimation error caused bythe acceleration interference and magnetic interference, a detailed analysis of the accelerometeron how to identify and handle the interference is made. The thesis proposes a new method foranti-interference, which use a small amount of random white noise to exchange themeasurement vector of the interference axial sensor. And the simulation result shows thisalgorithm has a good performance. Finally, make a research on the way of attitude control. Theway of calculation for target attitude and ship attitude is introduced. Through analyzing thestabilization principles of the three-axis framework derive a method of calculating the amountof control for framework. Simulation results show that the stability system meet the basicdesign designed requirements.The key of this thesis is how to get the relatively high precision antenna attitude through a low accuracy MEMS sensor. The original magnetic information measured by electroniccompass and information measured by MEMS accelerometer are used as measurement vectorof a Kalman filter, in order to correct the drift of MEMS gyro to ensure attitude accuracy. At thesame time the thesis propose a replacement for interfered measurement vector by using a smallamount of random white noise. It ensure that even acceleration interference and magneticinterference exits together, the system can still get a good estimated antenna attitude, whichprovides a high-precision angle reference for the stability control system. Finally, it makeantenna stabile through the movement of three-axis framework.