| The fiber optic gyroscope (FOG) has the advantages of good stability, low cost, wide dynamic range and quick start, so it has been widely used in military and civil fields.However, the FOG is very sensitive to the temperature change of environment, which will have effect of accuracy decrease on inertial navigation system (INS). In order to improve the output accuracy of the FOG, the gyro drift in varying-temperature environments should be compensated mathematically through temperature compensation method, and the compensation enable FOG output to keep stable and accurate. Therefore, the design for high-accuracy temperature compensation system for the FOG is very important to improve the FOG accuracy,and then the INS can meet the requirements about system accuracy.Aiming at the implementation of high-accuracy temperature compensation system for FOG, the high-accuracy temperature measuring system is designed and realized, to establish and improve the temperature compensation system. Firstly, according to the analysis of the functional and performance requirements, the overall scheme of the high-accuracy temperature compensation system for FOG is designed. Then using Pt1000 as temperature sensor, the temperature measurement circuit based on resistance comparison method is adopted to reduce the nonlinear error for temperature measurement system. Besides, the driving power sequences circuit is designed to eliminate the thermal electromotive force of temperature measurement circuit, and the self-heating effect can also be restrained.Combining resistance comparison method and the driving power sequences control, the high-accuracy temperature measurement system is accomplished. On the basis of the hardware design, a temperature correction method based on the piecewise linear fitting is designed to decrease the size of the temperature measurement system further. According to the noise characteristics of the temperature measurement output, a low-pass filter algorithm is designed to reduce the influence of random error on the temperature output accuracy.Based on the heating and cooling experiments, collecting datas about fiber loop temperature and FOG outputs synchronously, the major factors which affect FOG outputs are concluded through the analysis of the correlation between them. According to temperature of fiber loops and the FOG output error, the basic form of temperature compensation model is determined. Using the method of the piecewise high-order curve fitting, the temperature compensation system is designed based on the temperature of fiber loops and the FOG output error.After completing the temperature measuring circuit and the temperature compensation system, the main program can obtain the temperature signals by using use AD7608, and calculate and compensate the temperature through temperature correction method. Using temperature compensation model and the measured temperature data, the main program can calculate the real-time compensated results. When the communication module receives the navigation data, the main program decodes the data according to the communication protocol,and compensates the navigation data with the compensated results. After that, the main program encodes the compensated navigation data, and then the compensated navigation datas are sent to the navigation computer.At last, the high-accuracy temperature measuring system is tested for a long time by using low-temperature-drift and high-accuracy resistances. According to the heating and cooling experiments, the temperature compensation system is tested in terms of accuracy by using the measured temperature of fiber loops and the navigation data from FOG.The accuracy test results show that FOG output accuracy after temperature compensation can be ±0.05°/h. That is to say,temperature compensation system can be effective to restrain the FOG drifts caused by temperature, and then the INS accuracy can keep satisfactory. |
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