| Airborne satellite communication is a way of “Satcom on the move”. The key of this technology is that during the motion of aircraft, the servo system can isolate disturbance caused by the carrier movement, and the antenna can accurately track the target satellite all the time, so as to achieve the continuous and stable satellite communication in motion. In this thesis, the control technology of airborne satellite antenna tracking system is studied, and the key technology of the system is investigated.First of all, according to the operation requirements and performance indicators, the overall structure of the airborne satellite antenna tracking system is designed. The functions of three main subsystems, namely, antenna feeder and communication, servo control, control and display, are briefly explained. An azimuth-elevation-polarization three-axis strapdown stabilization platform based on airborne inertial navigation plus angle sensor plus satellite beacon and carrier AGC tracking scheme is proposed. Combined with the design of system solutions, the selection of servo-driven mechanism, onboard inertial navigation system, angle sensor and beacon receivers and other devices is complished.Secondly, the design of the hardware of peripheral circuit based on TMS320F2808 is presented. The software of the overall workflow, the central controller and the servo controller is developed. On this basis, the CAN bus and CANopen technology are applied to the communication and control of all parts of the system.Then, two kinds of initial searching strategy, namely, continuous scanning and variable step length scanning are proposed for this system. Combined with the characteristics of the airborne system, an automatic tracking strategy is proposed, which switches between the single program tracking and the step and program composite tracking. On the premise of meeting the tracking precision, this algorithm can improve the stability of the system. To suit all flight conditions, a corresponding strategy to recapture lost star is proposed.Finally, the controlled object model based on the driver, brushless DC motor, reducer and antenna turntable is built. Based on this model, two control algorithms are investigated, namely feedforward-PID and feedforward-nonlinear PID respectively. By MATLAB simulation, the time domain characteristics and disturbance attenuation capability of the two control algorithms are compared. With the two algorithms, the design of the program tracking is carried out, ensuring the tracking speed and tracking accuracy of the antenna. |
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