Modeling and Compensation Method for Temperature Error of FOG based on the SVM

The fiber optic gyroscope (FOG)based on Sagnac effect has became to one of the most important sensors in developing due to light in quality, high accuracy, compact in dimension and long life and has played a very important role in both military and civil use. It is the most difficult problem that the FOG has an obvious bias drift caused by temperature change and temperature grade, so its application is limited to a great extent. Fiber coil is one of the most critical components in FOG. Here, the characteristic of temperature error of the fiber optical coil was analyzed. At first, by studying the glass transition of coating adhesive in the fiber coil, the element model of the fiber coil with the glass transition of coating adhesive in FOG was built. Then the discrete mathematics model of SHUPE error with the glass transition of coating adhesive in FOG was built. Finally, based on the temperature models mentioned above, the effects caused by the glass transition of coating adhesive on temperature performance of fiber optic gyroscope were analyzed. Theoretical analysis and experimental results show that effect caused by the glass transition of coating adhesive had seriously affected the temperature performance of FOG. By optimizing the glass transition temperature of coating adhesive, the SHUPE error of fiber coils can be reduced. At the same time, the amplitude uniformity of the SHUPE error can be improved greatly to reduce the difficulty in temperature compensation.

Since the advantages of high precision, large dynamic range in angular velocity measurement, Fiber Optic Gyroscopes (FOGs) are recently proposed to be used as angle measuring instrument. However, in dynamic testing condition like sway, the outputs of FOGs contain inevitable angular velocity measurement error, harming angle measuring accuracy. Therefore, FOGs must be calibrated before using. In this paper, we first propose a high-precision and non-contact angle measurement method with dual-Laser Doppler Vibrometers (d-LDVs) to calibrate the angle measurement error of FOGs in sway condition. Firstly, we verify the accuracy and dynamic range of this proposed angle measurement method by using a high-precision rotary table as an angle benchmark. Experimental results indicate that this method can reach the dynamic angle measurement with the range of ±10°, and the maximum angle measurement error is less than 0.0088°. Secondly, in order to calibrate the angle measuring error of FOGs, we establish an angle calibration system for FOGs based on d-LDVs under sway condition. Experimental result shows that the dynamic angle measurement error of the FOG caused by dynamic environment is less than 0.015°. Because of the zero drift of angular velocity, integral angle of the FOG shows angle drift, and the maximum angle drift is 0.06° (during 30s).

A Star Sensor based Fiber Optical Gyroscope Error Separation method (SSFES) was proposed, which can be applied in the Fiber Optical Gyroscope (FOG) performance evaluation and fault diagnosis for the space-borne Inertial Navigation System (INS) & Celestial Navigation System (CNS) combined navigation system. The method takes the satellite rotational angular rate and the attitude quaternion to separate the long-term drift component from the FOG output and provides the useful information for FOG error compensation and model construction. The output quaternion of the star sensor was utilized to reconstruct the satellite rotational angular rate information, which was then used to separate the error component from the FOG output. Simulations have been carried out to verify the method and have shown that the error component of FOG output can be extracted efficiently by SSFES and the algorithm is easy to be performed by the onboard computers.

Error analysis and compensation method of displacement measurements based on reflection projection imaging

This paper proposes a joint temperature drift compensation method for dual-channel interferometric fiber-optic gyroscopes (IFOGs) to mitigate the impact of temperature variations on modulation depth and measurement performance. The proposed method establishes a temperature-dependent modulation depth model and develops a real-time compensation strategy that dynamically adjusts the modulation voltage to maintain optimal modulation depth. To ensure consistency between the two sensing channels, a joint compensation method is implemented, incorporating power balancing and residual correction. Experimental results demonstrate that this method effectively suppresses temperature-induced drift, improving sensitivity by 2.5 times, expanding the detection bandwidth from 0.3 Hz–50 Hz to 0.01 Hz–50 Hz, and enhancing bias instability (BI) by over 2.7 times. By significantly improving the detection bandwidth and stability of dual-channel IFOGs under temperature variations, this compensation method offers a promising solution for high-precision measurement applications.

Temperature sensitivity of a fiber coil made up of hundreds to thousands of meters of fiber is an important parameter determining the performance of fiber optical gyroscope (FOG). A method based on frequency-modulated continuous-wave (FMCW) is proposed to measure the temperature sensitivity of fiber coil, and the result indicates that it is larger that that of the fiber itself, and surprisingly with the opposite polarity, so it provides some useful information to deeply understand the properties of the fiber coil, as well as for the improvement of FOG performance over temperature.

In this work, the fiber optic gyroscope (FOG) with an elliptic fiber coil (EFC) is applied to the inertial measurement of petroleum well trajectory for the special condition of the borehole diameter limitation in the inclinometer while drilling (IWD). The three-dimensional (3D) Shupe error mathematical model and finite element model of the EFC are established by the quadrupole symmetrical technique, which is based on the Shupe effect of fiber coil. Then, the simulation experiments and the temperature experiments of the EFC are carried out to verify the correctness of the mathematical model. Under this prerequisite, the influence of the structure parameters of the EFC on the Shupe error is analyzed. In order to compare the rotation rate error between the EFC and the circular fiber coil (CFC), the temperature experiments of the EFC and the CFC are carried out with the same temperature excitation when the fiber length, the layers of fiber coil, and the radius of fiber coil of the EFC are the same as those of the CFC. The results show that the bias stability of the EFC is 35% to 39% smaller than that of the CFC before the temperature compensation, and after the temperature compensation, the bias stability of the EFC is 49% to 70% smaller than that of the CFC.

Background/Objectives: The main objective of this paper is to perform a comparative discussion in gyro parameters for three cases: (i) V2π (vary)&Vπ/2 (constant), (ii) Vπ/2 (vary) and V2π (constant) and (iii) both V2π and Vπ/2 are varying simultaneously. Methods/Statistical Analysis: Fibre optic gyroscope has to be operated in closed-loop approach to achieve the inertial-grade-performance. The Closed-Loop Interferometric Fibre Optic Gyroscope (CLIFOG) system depends upon ramp voltage (V2π of IOC) and square-wave biasing signal frequency (f bias ). The digital-phase-ramp-function is used as feedback to system and makes gyro to null condition. The biasing signal voltage (Vπ/2) is 1/4 th of ramp voltage (V2π). If there are any variations in ramp and biasing signal voltages, then it introduces variations in gyro performance. Results: The ramp voltage (V2π) and square wave biasing signal voltage (Vπ/2) is increased from 1% to 10%, decreased to 1% to 10% and performed the various tests for three cases. From results, it was noted that: (i) When V2π is varying and Vπ/2 is kept constant, the scale-factor change is increasing as the error in the signal voltage is also increases. (ii) When V2π is kept constant and Vπ/2 is varying, the change in scale-factor is very minute and maintains the scale-factor linearity. (iii) While varying both V2π and Vπ/2 voltages simultaneously, the device is not responding accordingly as the error is increasing and also scale-factor is out of range subsequently. The effects on the CLIFOG system are described with the derived values in terms of bias and scale-factor. The gyro performance is very sensitive with respect to V2π variations and the percentage error is high in gyro output, but very less effect due to Vπ/2 variations when the ramp voltage (V2π) is constant. Conclusion/Application: The Closed Loop Interferometric Fiber Optic Gyroscope (CLIFOG) system requires a proper resetting of ramp voltage (V2π) in order to avoid the bias and scale factor instabilities.

The advantages of mechanical gyros, such as high precision, endurance and reliability, make them widely used as the core parts of inertial navigation systems (INS) utilized in the fields of aeronautics, astronautics and underground exploration. In a high-g environment, the accuracy of gyros is degraded. Therefore, the calibration and compensation of the gyro G-sensitivity coefficients is essential when the INS operates in a high-g environment. A precision centrifuge with a counter-rotating platform is the typical equipment for calibrating the gyro, as it can generate large centripetal acceleration and keep the angular rate close to zero; however, its performance is seriously restricted by the angular perturbation in the high-speed rotating process. To reduce the dependence on the precision of the centrifuge and counter-rotating platform, an effective calibration method for the gyro g-sensitivity coefficients under fiber-optic gyroscope (FOG) monitoring is proposed herein. The FOG can efficiently compensate spindle error and improve the anti-interference ability. Harmonic analysis is performed for data processing. Simulations show that the gyro G-sensitivity coefficients can be efficiently estimated to up to 99% of the true value and compensated using a lookup table or fitting method. Repeated tests indicate that the G-sensitivity coefficients can be correctly calibrated when the angular rate accuracy of the precision centrifuge is as low as 0.01%. Verification tests are performed to demonstrate that the attitude errors can be decreased from 0.36° to 0.08° in 200 s. The proposed measuring technology is generally applicable in engineering, as it can reduce the accuracy requirements for the centrifuge and the environment.

In order to reduce the relative intensity noise (RIN) in the interferometric signal of the fiber optic gyroscope (FOG), an adaptive noise subtraction method is presented, which aims to overcome to the drawbacks that the fixed delay time and gain of the digital noise subtraction method. The drawbacks will make the performance of FOG to be degraded greatly in the changing environment. In the paper the adaptive noise subtraction system based on the recursive least squares algorithm (RLS) is formed in FPGA, in which the interferometric signal is regarded as the signal source, and RIN in the free end of the optical fiber coupler of FOG is looked as the noise reference signal. The two critical parameters that minimum delay time and its varying range result from measuring the minimum and maximum delay times of the interferometric signal in a certain temperature range. The off-line and on-line temperature experimental results verify the capability of adapting to the environmental temperature. DOI : http://dx.doi.org/10.11591/telkomnika.v12i1.3373

The radiation effects of opto-electronic devices used in fiber-optic gyroscope are introduced in this paper. The radiation characteristics of opto-electronic devices are studied by performing total dose radiation experiment, and the influences of anti-radiation capability of opto-electronic devices on the performance of fiber-optic gyroscope are analyzed. The research results show that SLD (superluminescent diode) source, PIN detector, Y wave-guide and fiber optic coupler are not sensitive to the radiation of γ rays, while the polarization maintaining optical fiber is comparatively sensitive to radiation. It is found that C polarization maintaining optical fiber has the strongest anti-radiation capability to satisfy the space application demand of fiber-optic gyroscope.

The pure Shupe effect is substantially reduced in a fiber optic gyroscope (FOG) with symmetrical windings. However, the effect of the temperature-induced nonuniformity of the stress in the coil depends on the mean temperature derivative (T-dot). Research on precision winding technology has discovered that the symmetry of optical fiber rings affects the temperature performance of fiber optic gyroscopes. Optical fiber rings with good symmetry also have good temperature performance. This paper first establishes a temperature drift model of optical fiber rings that includes the Shupe effect and T-dot effect and then uses finite element simulation to analyze the drift error of optical fiber rings in a variable temperature environment. Analysis shows that this drift is caused by the variation and uneven distribution of the fiber length and the refractive index in the positive and negative winding of the optical fiber ring, which results in a residual phase difference that is directly related to the symmetry of the optical fiber ring. Simulation and analysis show that balancing the residual phase difference of the optical fiber ring can be achieved by cutting the length of the optical fiber ring at both ends. This paper uses optical frequency domain reflectometry (OFDR) technology to precisely test the symmetry of the optical fiber ring, ensuring accurate adjustment of the lengths at both ends of the optical fiber ring. Experimental tests on two gyroscopes have shown that the optical fiber ring with a smaller drift error can be obtained after testing and adjusting its length. The experimental data indicates that the bias stability of two laboratory gyros are increased by 23.6% and 18.1%, and the bias range are reduced by 22.4% and 30.0%.

For a fiber optic gyroscope, thermal deformation of the fiber coil can introduce additional thermal-induced phase errors, commonly referred to as thermal errors. Implementing effective thermal error compensation techniques is crucial to addressing this issue. These techniques operate based on the real-time sensing of thermal errors and subsequent correction within the output signal. Given the challenge of directly isolating thermal errors from the gyroscope’s output signal, predicting thermal errors based on temperature becomes necessary. To establish a mathematical model correlating the temperature and thermal errors, this study measured synchronized data of phase errors and angular velocity for the fiber coil under various temperature conditions, aiming to model it using data-driven methods. However, due to the difficulty of conducting tests and the limited number of data samples, direct engagement in data-driven modeling poses a risk of severe overfitting. To overcome this challenge, we propose a modeling algorithm that effectively integrates theoretical models with data, referred to as the TD-model in this paper. Initially, a theoretical analysis of the phase errors caused by thermal deformation of the fiber coil is performed. Subsequently, critical parameters, such as the thermal expansion coefficient, are determined, leading to the establishment of a theoretical model. Finally, the theoretical analysis model is incorporated as a regularization term and combined with the test data to jointly participate in the regression of model coefficients. Through experimental comparative analysis, it is shown that, relative to ordinary regression models, the TD-model effectively mitigates overfitting caused by the limited number of samples, resulting in a substantial 58% improvement in predictive accuracy.

Piezoresistive pressure sensors have broad applications but often face accuracy challenges due to temperature-induced drift. Traditional compensation methods based on discrete data, such as polynomial interpolation, support vector machine (SVM), and artificial neural network (ANN), overlook the thermal hysteresis, resulting in lower accuracy. Considering the sequence-dependent nature of temperature drift, we propose the RF-IWOA-GRU temperature compensation model. Random forest (RF) is used to interpolate missing values in continuous data. A combination of gated recurrent unit (GRU) networks and an improved whale optimization algorithm (IWOA) is employed for temperature compensation. This model leverages the memory capability of GRU and the optimization efficiency of the IWOA to enhance the accuracy and stability of the pressure sensors. To validate the compensation method, experiments were designed under continuous variations in temperature and actual pressure. The experimental results show that the compensation capability of the proposed RF-IWOA-GRU model significantly outperforms that of traditional methods. After compensation, the standard deviation of pressure decreased from 10.18 kPa to 1.14 kPa, and the mean absolute error and root mean squared error were reduced by 75.10% and 76.15%, respectively.

This paper introduces a high-precision photonic crystal fiber optic gyroscope for space application. The overall design scheme of the gyro is proposed and the optimized small-diameter low loss photonic crystal fiber used for gyroscope is presented. Finally, products and test data of the new generation high precision photonic crystal fiber optic gyroscope products are given.