The GPS Simulator Design Based On Real-time System

In recent years, due to the rapid development and extensive application of unmanned aerial vehicle(UAV) in military and civil areas, the future market of the UAV is getting more and more attention from all countries. In the development of UAV, the hardware in the loop simulation of UAV's navigation control system has become an important stage in the research and development process. In the simulation of flight control system, how to simulate the position information of UAV in the air is an important problem which must be solved in the whole system. In view of this, a global positioning system(GPS) simulator is designed for solving the problem in this paper.The modern computer simulation technology is employed in this paper to simulate the real flight of UAV by using real-time simulator loading dynamic model. Then the principle of the GPS and the characteristics of the output data format of the airborne GPS receiver are studied in depth. A framework of GPS simulator system is presented, and the functions of each module in the framework are described in detail.The development and design of the simulator is divided into three modules, which are the track generation module, the data processing module and the communication interface module. The track generation part uses the DS1103 real-time simulation machine of German dSPACE company as the control object of the UAV, and completes the whole process of modeling the UAV dynamic model to the real time code generation. After the analysis of the RINEX original ephemeris reference data, the data processing module establishes GPS constellation model and calculates the constellation position on orbit in real time under the MATLAB/Simulink development environment. According to the location of the UAV from the track generation module, the data processing module is used to judge the visible star and select the best visible star. The communication interface module is designed to complete the serial communication program design based on S-Function, package the relevant parameters calculated from the data processing module in accordance with the GPGGA and GPRMC protocol statements, and send the above date to the navigation control system through the RS232 serial port.