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Article considers the development of a temperature calibration method for fiber-optic gyroscopes that are a part of a gyrostabilization subsystem of multi-spectral scanning system hardware.
Теги: fiber-optic gyroscopes temperature calibration волоконно-оптические гироскопы температурная калибровка
JCS "ELSY" has been developing of multipurpose gyro-stabilized optical-electronic observation system – MOS (Fig.1), which are part of unmanned aerial vehicles, helicopters, aircraft, marine and river vessels and other vehicles. Optical-electronic observation system contains a gyrostabilization subsystem (including gyroscopic sensors module). The basis of gyroscopic sensors module are fiber-optic gyroscopes (FOG) and electronic processing unit.
The main requirement for optical-electronic observation systems is gyrostabilization accuracy. As change of temperature of FOG in the course of their work strongly influence their operational characteristics. There are problems of temperature calibration of the gyroscopic sensors module before developers.
In full-scale climatic testing could not be recreated all combinations of variational of environmental changes. MOS developers are using a mathematical model of FOG capable to describe the functioning of the device to replace the multivariate natural tests. Earlier model does not take into account the effect of wide range temperature changes. Achievement of high accuracy of gyrostabilization in the wide range of temperatures, requires careful research of temperature components of drift of zero and a mean square deviation of noise of fiber-optical gyroscopes.
Gyroscope output signal contains multiplicative and additive errors. The multiplicative error depends on temperature distortion of scale factor. Additive error contains two temperature factors: zero drift and noise.
Gyroscope output signal:
Uout = k(T) · ω + Ud(T) + N(T), (1)
where UOUT [V] – output voltage; Ud(T) [V] – zero drift; k(T) [V/deg/s] – scale factor; ω [deg/s] – angular velocity; N(T) [V] – temperature noise.
Zero drift in FOG d is caused by several reasons:
interference of analog circuits;
shift of operational amplifiers;
shift of a spectra of a superluminescent light-emitting diode;
two-refraction modulation in the modulator;
Faraday’s magnetooptical effect;
thermal expansion of fiber in the interferometer.
Heating of all the optical and electrical components leads to an increase of zero drift in output signal. The gyroscope noise is mainly caused by photodetector noise and analog circuits noise. Temperature drift of zero signal is the main error that must be well explored.
Experimental studies were made to obtain parameters of the temperature (T) dependence of noise and zero drift. To simulate the effect of zero drift made the approximation of average output signal:
Ud1(T) = 1,023 · 10−7 · T2 + 2,616 · 10−6 · T + 0,000307;
Ud2(T) = 0,853 · 10−7 · T2 – 7,483 · 10−6 · T – 0,000002;
Ud3(T) = 3,049· 10−7 · T2 + 3,178 · 10−6 · T + 0,000071;
σ1(T) = 4,26 · 10−6 · T + 0,000012;
σ2(T) = 1,77 · 10−6 · T + 0,000037;
σ3(T) = 2,45 · 10−6 · T + 0,000061.
These expressions were received in the temperature range from 0 °C to +48 °C. Researches in the field of negative temperatures weren’t conducted as FOG and the electronic module of processing work in the multipurpose gyro-stabilized optical-electronic observation system tight case with heating. In this block temperature fall lower than 0 °С isn’t provided. Model was developed using Simulink, which is part of MATLAB.
Conclusion
For replacement of natural tests of multipurpose gyro-stabilized optical-electronic observation system developers used earlier existing FOG mathematical model. However, earlier used model didn’t consider change of drift of zero and noise mean square deviation from temperature. Therefore the task to develop new simulation model in which dependences of drift of zero and mean square deviation of noise of FOG in the wide range of temperatures are considered was set.
The given simulation model considers dependence of drift of zero and noise mean square deviation on temperature that allows to increase the accuracy of gyrostabilization of multipurpose gyro-stabilized optical-electronic observation system in a wide interval of temperatures for 30%.
The main requirement for optical-electronic observation systems is gyrostabilization accuracy. As change of temperature of FOG in the course of their work strongly influence their operational characteristics. There are problems of temperature calibration of the gyroscopic sensors module before developers.
In full-scale climatic testing could not be recreated all combinations of variational of environmental changes. MOS developers are using a mathematical model of FOG capable to describe the functioning of the device to replace the multivariate natural tests. Earlier model does not take into account the effect of wide range temperature changes. Achievement of high accuracy of gyrostabilization in the wide range of temperatures, requires careful research of temperature components of drift of zero and a mean square deviation of noise of fiber-optical gyroscopes.
Gyroscope output signal contains multiplicative and additive errors. The multiplicative error depends on temperature distortion of scale factor. Additive error contains two temperature factors: zero drift and noise.
Gyroscope output signal:
Uout = k(T) · ω + Ud(T) + N(T), (1)
where UOUT [V] – output voltage; Ud(T) [V] – zero drift; k(T) [V/deg/s] – scale factor; ω [deg/s] – angular velocity; N(T) [V] – temperature noise.
Zero drift in FOG d is caused by several reasons:
interference of analog circuits;
shift of operational amplifiers;
shift of a spectra of a superluminescent light-emitting diode;
two-refraction modulation in the modulator;
Faraday’s magnetooptical effect;
thermal expansion of fiber in the interferometer.
Heating of all the optical and electrical components leads to an increase of zero drift in output signal. The gyroscope noise is mainly caused by photodetector noise and analog circuits noise. Temperature drift of zero signal is the main error that must be well explored.
Experimental studies were made to obtain parameters of the temperature (T) dependence of noise and zero drift. To simulate the effect of zero drift made the approximation of average output signal:
Ud1(T) = 1,023 · 10−7 · T2 + 2,616 · 10−6 · T + 0,000307;
Ud2(T) = 0,853 · 10−7 · T2 – 7,483 · 10−6 · T – 0,000002;
Ud3(T) = 3,049· 10−7 · T2 + 3,178 · 10−6 · T + 0,000071;
σ1(T) = 4,26 · 10−6 · T + 0,000012;
σ2(T) = 1,77 · 10−6 · T + 0,000037;
σ3(T) = 2,45 · 10−6 · T + 0,000061.
These expressions were received in the temperature range from 0 °C to +48 °C. Researches in the field of negative temperatures weren’t conducted as FOG and the electronic module of processing work in the multipurpose gyro-stabilized optical-electronic observation system tight case with heating. In this block temperature fall lower than 0 °С isn’t provided. Model was developed using Simulink, which is part of MATLAB.
Conclusion
For replacement of natural tests of multipurpose gyro-stabilized optical-electronic observation system developers used earlier existing FOG mathematical model. However, earlier used model didn’t consider change of drift of zero and noise mean square deviation from temperature. Therefore the task to develop new simulation model in which dependences of drift of zero and mean square deviation of noise of FOG in the wide range of temperatures are considered was set.
The given simulation model considers dependence of drift of zero and noise mean square deviation on temperature that allows to increase the accuracy of gyrostabilization of multipurpose gyro-stabilized optical-electronic observation system in a wide interval of temperatures for 30%.
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