In recent years, the large volume, high cost, and high power consumption of fiber optic gyroscopes composed of various discrete devices have limited their application in various micro inertial navigation systems. This paper proposes a fiber optic gyroscope based on integrated optoelectronic devices. Compared with fiber optic gyroscopes based on discrete components, fiber optic gyroscopes based on integrated optoelectronic devices significantly reduce their volume despite limited accuracy degradation, and are expected to be applied in integrated fiber optic gyroscopes.
With the development of micro and small aircraft, unmanned systems, autonomous driving, wearable human navigation technology, missile guidance, and other fields. Accuracy is no longer the only core indicator of inertial navigation systems. Low cost, size, quality, and power (CSWaP) have become the key to enhancing the competitiveness of inertial technology products. Due to the large size and independent packaging of optical components, it is difficult to improve the CSWaP comprehensive performance of fiber optic gyroscopes (FOGs) under traditional solutions. Currently, using integrated optical technology to realize the integration of FOGs is the main way to reduce the comprehensive indicators of CSWaP of FOGs. Integrated FOGs refer to FOGs that use integrated optical chips to partially or completely replace optical devices of traditional FOGs. In this article, we propose a design scheme for a specialized integrated device of three-axis FOGs, which can achieve the integration of the main optical components of the interferometric fiber optic gyroscope optical path. It is of great significance for promoting the development process of miniaturization, lightweight, integration, low power consumption, and low cost of FOGs.
Firstly, the requirements of ultra-high precision gyroscope for light source are analyzed. Ultra-high precision fiber optic gyroscope (FOG) is used in long-term inertial navigation system for naval vessels, which requires high precision, stability of scale factor and nonlinearity of scale factor. The stability of the average wavelength of the light source directly affects the stability of the scale factor of the FOG. The high power output of the light source combined with other noise reduction methods can improve the signal-to-noise ratio of the FOG, thereby improving the detection accuracy. The coherence of light source spectrum will affect the coherent noise of the FOG, the symmetry of spectrum will affect the nonlinearity of scale factor, and the spectral width will affect the noise level. Therefore, ultra-high precision FOG requires high power, high wavelength stability, large spectral width, hyperspectral symmetry and low coherence light source. Second, an ASE source for ultra-high precision FOG is proposed in this paper. In terms of optical path, the optical path structure of ASE light source and the means to improve the average wavelength stability of the light source are analyzed. Two-stage Erbium fiber structure is used to obtain high power output. Faraday rotating mirror is used to reduce the polarization-dependent gain in Erbium fibers. High stability of average wavelength is achieved by optimizing erbium fiber parameters and pump power. The non-subpeak Gauss spectrum of the coherence function is chosen as the spectral scheme. In the design of the filter, the orthogonal experiment and hardware-in-the-loop simulation are used to optimize the filter parameters and perform the whole spectrum shaping filtering. The output spectrum width is over 20 nm, which is much wider than 7-13 nm of traditional filtering method,and reduces the noise of gyro noise. In the drive circuit, the high stability temperature control of the pump is realized. By controlling the temperature characteristics of the feedback loop devices, the power stability of the light source is greatly improved by using the power feedback mode. The ASE light source designed above can provide power output of more than 30 mW. The wavelength stability is less than 5 ppm in the whole temperature range, and less than 1 ppm at the constant temperature. The power variation is less than 1%, and the spectrum width of output is more than 20 nm. It is an ideal light source for ultra-high precision fiber optic gyroscope..
With the increasing demand of navigation and positioning services, the accuracy and safety of traditional navigation system have been limiting factor of future application. The development of quantum technology brings hope to the research and development of a new generation of navigation system. In this paper, the application of quantum technologies in fiber optic gyroscope is introduced and analyzed.
The temperature drift causes the zero-bias drift of the fiber optic gyroscope to show complex nonlinear changes, which seriously restricts the measurement accuracy of the fiber optic gyroscope. Therefore, it is necessary to establish an accurate temperature compensation model to compensate for the temperature drift of the fiber optic gyroscope.In order to effectively improve the output accuracy of the fiber optic gyroscope under the condition of the full temperature range, the static full temperature bias test of the fiber optic gyroscope is first designed to obtain the bias data of the fiber optic gyroscope under the temperature change condition of -40℃~60℃. Secondly, on the one hand, a polynomial regression model is gradually established with temperature, temperature change and multiple powers as independent variables. On the other hand, the RBF neural network model is established after screening the input variables with the MIV algorithm. Finally, two models are used to achieve zero-bias temperature compensation. According to the compensation results, both can effectively improve the full temperature output accuracy of the fiber optic gyroscope. Compared with the polynomial regression model, the RBF neural network model can identify temperature drift more effectively and accurately, and greatly improve the output accuracy of the fiber optic gyroscope in the full temperature range.
The improvement in the performance of fiber optic gyroscope raises increasingly high standard on the performance of potting adhesive for optical fiber coil. It cannot only enable the stability of coil potting, but also maintain long-term stability under complex environmental stress. In order to meet the indicators of temperature performance of optical fiber coil, we have prepared the acrylic matrix potting adhesive via UV photo-curing by grafting the hard-segment chain containing benzene ring with polyurethane acrylate(PUA) as the matrix, studied the influence of resin matrix, photoinitiator and active diluent on the UV curing of potting adhesive for optical fiber coil, and went into in details the indicators including the curing rate, modulus and glass transition temperature performance of potting adhesive so as to provide experimental support for obtaining the best matched UV potting adhesive curing system. In this study, we have characterized the molecular structure of potting adhesive via infrared spectroscopy, studied the thermomechanical properties of potting adhesive by thermal analysis, and finally verified the process stability of potting adhesive and the temperature characteristics of coil through coil winding and potting and curing.
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