Research And Design Of Servo System For Vehicle Mobile Satellite Communication

Along with the growing demand for communication technology, mobile satellitecommunication has been acquired more and more concern and attention by experts andscholars at home and abroad. Vehicle mobile satellite communication system (i.e., On-The-Move system) can transmit the information such as voice, data and image, in the process ofmovement in real time, large capacity and uninterrupted manner.This thesis analyses and studies the servo control in vehicle mobile satellitecommunication system, and designs the key technologies such as the initial acquisitionalgorithm, the re-acquisition algorithm and the auto-tracking and controlling algorithm.Besides, these algorithms designed in this thesis are proved reasonable and efficient throughthe experimental simulation and the actual tests.Firstly, this thesis describes the overall structure of the system design. According to therequirement of system design, two-axis mechanical structure and three-axis tracking schemeis selected. Then the system mechanical structure is introduced, and the system performancerequirements are given. The hardware design includes the bus topology design, the circuitdesign and CAN bus controller system design, and the software design mainly includes thesoftware development environment and the overall structure design of system software.Secondly, the initial acquisition algorithm is researched and designed in this thesis.Through calculation and derivation, geocentric coordinate system, geocentric coordinatesystem and carrier coordinate system, and the mutual concersion formula were described.Besides, the angle formulas of azimuth angle, elevation angle and polarization angle insatellite alignment are deduced. After introduced the principle of the initial acquisitionalgorithm, the system initial acquisition scheme and sesrch processes are designed. Moreover,the improved acquisition algorithm based on the traditional algorithm, the theoretical analysisand simulation experiments are conducted.Thirdly, this thesis discusses and designs the system re-acquisition algorithm. Theprinciple and the system implementation of conically scanning algorithm and two-dimensional step tracking algorithm are introduced, the corresponding improvement has beentoken. In addition, this thesis describes the commonly used helical scanning algorithm andline-by-line scanning algorithm, and designs the spiral branch scanning algorithm in thesystem re-acquisition stage considering the advantages and disadvantages of variousalgorithms and systems in practice.Finally, this thesis has conducted the reasch of the system automatic tracking algorithm, and designed the establishment of the servo system model. Besides, the mathematical modelof the motor is designed according to the actual motor parameters. On the basis of the overallcontrol system mathematical model, the traditional PID algorithm and the feed-forwardcontrol algorithm are studied, and the feedforward-PID control algorithm is designedcombined with the actual system. Through the analysis of the current system performanceand the existing problems, this thesis designs the automatic tracking algorithm, and theeffectiveness of the algorithm is proved by introducing the correction link and combined withthe experimental simulations and actual test results.