In order to meet the temperature performance requirements of high-precision FOG, the Shupe coefficient of the optical fiber coil must be further reduced. The generation of Shupe error is not only related to the rate of change of temperature with time, but also related to the rate of change of thermal stress with time. In this paper, the effects of thermal conductivity and internal stress of the potting adhesive on the Shupe error of the optical fiber coil were carried out. By designing a hyperbranched molecular structure, the curing stress of the UV potting adhesive was greatly reduced, and a rigid-flexible block structure was prepared by adjusting the formulation components to obtain high modulus (Eˊ) and high glass transition temperature (Tg) performance, which greatly improved the full temperature stability and long-term reliability of the potting adhesive. The potting adhesive is doped with high thermal conductivity particles to obtain high thermal conductivity, reduce the temperature gradient inside the optical fiber coil, and improve the full temperature performance of the coil. The results showed that the glass transition temperature of the developed high-precision optical fiber coil UV potting adhesive is higher than 100℃, and the Young's modulus is higher than 2000MPa. The peak-to-peak value of the coil Shupe is 0.1°/h. Through research, low stress, high thermal conductivity potting adhesive can effectively reduce the Shupe error of the high-precision optical fiber coil, improve the full-temperature performance of the coil, and realize the long-term stability and reliability of the FOG.
The development of high precision fiber optic gyroscope (HFOG) is of great strategic significance to a country's industrial and national defense science and technology. Optical fiber coil is the key to guarantee the accuracy and long-term stability of HFOG, and the adhesive is an important factor for the stability of optical fiber coil performance. In order to improve the temperature characteristics of HFOG, this study carried out the research on the technology of high thermal conductivity adhesive doped with high thermal conductive filler to improve its thermal conductivity (κ), and prepared a high thermal conductivity coil potting adhesive with excellent heat transfer and heat dissipation performance. By designing the composition ratio and block molecular structure with alternating soft and hard segments, the balance of glass transition temperature (Tg) and Yong’s modulus (Eˊ) was obtained, which can make the temperature field distribution of the optical fiber coil more uniformly, reduce the stress in the coil after curing, reduce the coil temperature errors. The above studies suppress the temperature drift and improve the overall accuracy of HFOG.
With the change of working time and environmental conditions, the performance of optical fiber coil has deteriorated, which seriously affects its long-term stability. In recent years, the performance of fiber optic gyroscope(FOG) has been continuously improved, and the requirements for adhesive of fiber optical coil have become higher and higher. It is required not only to meet the stability of coil potting, but also to resist high and low temperature environment for a long time during operation of FOG. In view of this, the study in the environmental stress effects of optical fiber coil adhesive was carried out. Based on optical fiber coil, this paper introduces the environmental stress and its influence mechanism of polymer materials aging, and focuses on the optical fiber coil adhesive aging behavior, as well as analyses the physical and chemical properties of adhesive. On basis of this, environmental stress tests were carried out, and the physical and chemical properties of adhesive were obtained. The experiment and analysis results showed that the glass transition temperature will significant transfer under excessive ultraviolet exposure or a long time high temperature of 85degree Celsius and low temperature of -45degree Celsius, and the adhesive viscosity significantly increased in high humidity environment. Under the comprehensive effect of various environmental stress, the adhesive properties will changed and further affect the stability of optical fiber coil.
As high-precision fiber optic gyroscopes, especially three-axis high-precision fiber optic gyroscopes, face harsh electromagnetic environments, Y-junctions have become a key component that affect the precision of fiber optic gyroscopes. A high extinction ratio Y-junction is fabricated to suppress the polarization mode coupling of the fiber optic gyroscope and reduce the noise of the fiber optic gyroscope. The experimental results show that the above methods effectively solve the effect of the deterioration of the precision of the fiber optic gyroscope caused by the Y-junction.
With the rapid development of the fiber optical gyroscope technology and its widely applies, the multi-axis Fiber Optical Gyroscope (FOG) such as the triaxial FOG and its system are popular more and more.[1-2] For the requirement of less weight and less size,[2] the multi-axis FOG needs higher electromagnetic structure design skills and more critical devices compared with uniaxial FOG. The Z axis of some triaxial FOGs occur the problem of the bias instability over tolerance, which is a real engineering case in our development process. In this paper experiments are carried out after the influence factors are analyzed. Results show that the modulation of the Z axis is interfered by the other two axes. There are three test steps in the experiment including the optical unit test, the modulator test and the modulator shield test with different materials. A simulation of the original shield structure is applied in order to find the structure defects. Two defects are found on the base of the analysis of the electromagnetic structure check. The main defect is that there is a hollow structure on the top of the Z axis in the system which causes extra electromagnetic circuit from the other two axes. The other defect is that each axis is exposed under complex circumstance with less modulator shield. The modulator with less shield has the merit of less thermal stress owing to the free contraction between the metal packaging and the modulator. In our triaxial FOG system, the modulator shield structure inherits from the uniaxial FOG with less shield, in order to decrease the thermal stress. As we know, in the uniaxal FOG the modulator will still robustly work under a clean electromagnetic circumstance, even there is no shield upon the modulator. However, in the multi-axis FOG there are obvious crosstalk interference between the different axes, when all axes are working together with a close frequency. Based on the experiments and the analysis, the following design principles are given. Firstly, the thermal factors, the vibration factors and the electromagnetic factors should be considered at the same time when the modulator shield is designed. Secondly, the Fe-Ni material has better shield effect than the common metal like Aluminum. Thirdly, there are two kinds of resins, the hard buffer and soft buffer, to connect the Y-junction fiber tail and the metal capsulation. This paper is of great use to the engineering of the multi-axis fiber optical gyroscopes and the fiber optical gyroscope system applications.
Based on the Sagnac effect, the small changes in thermally induced stresses and microcosmic size of optical fiber coil can cause the drift of the Shupe error and scale factor of fiber optic gyroscope (FOG). As polymer functional resin represents a high proportion in optical fiber coil, its physical and chemical properties determine largely the thermally induced stresses and dimensional stability of the coil, thus influencing the performance of FOG. Given the demands for the long-term stability and temperature characteristics of FOG, this paper studies the influence of molecular chain structure and thermal conductivity of polymer functional resin for optical fiber sensing on FOG. The experimental results suggest: high thermal conductivity can reduce the thermal induced stresses of polymer functional resin of reticular molecular structure, greatly improving the zero bias stability of FOG at all temperature; hyperbranched molecular structure reports outstanding creep-resistant characteristics thanks to the significantly reduced internal free volume of optical fiber coil after encapsulation and insignificant dimensional changes at all temperatures, thus ensuring long-term stability of the scale factor of FOG.
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.
The fiber optic gyroscope has become to one of the most important sensors in developing due to light in quality, high accuracy, compact in dimension and long life[1-4]. These features have developed new applications of the gyroscope not only in conventional aerospace application area but also in industrial application area, such as control and navigations of unmanned vehicles, antenna/camera stabilizers, and so on. More and more FOGs have been applied in all kinds of satellites for attitude control. With the great technology progress on fiber optic gyroscopes in recent years, the reliability of fiber optic gyroscopes has been focused on. The fiber coil, as one of the most critical components in fiber optic gyroscope,its reliability directly determines the reliability of the fiber optic gyro. This paper uses the Bayesian estimation method to study the reliability of the fiber coil. Aiming fiber optic gyroscope fiber coil Failure Data Reliability analysis of the problem, on the basis of analyzing the failure mode, select Weibull distribution as its life mode, the estimated time of each detection without failure data using Bayesian theory failure rate, and thus the estimated model parameters fiber coil reliability. The Bayesian estimation method combined with experience information greatly reduces the number of test samples, and to overcome the shortcomings of the traditional reliability evaluation method relies on failure data, has a high value in engineering applications. This estimation method shows its significance in saving test costs and time.
Fiber optic gyroscope (FOG) is a multi-technology product which integrates optics, mechanics and electricity. It has the advantages of high reliability, long life, light weight, small size and "all solid state". It has been widely used in military and civil fields such as sea, land, air, sky and submarine, and has become the mainstream gyroscope in the field of inertial technology. With the widespread application of FOG, the degradation of its key performance indicators gradually emerges as time goes on. Therefore, it is urgent to obtain the reliability index of FOG. In order to obtain reliable reliability index of FOG with time and cost saving as much as possible, it is necessary to choose reasonable acceleration test method, acceleration model and life distribution model to study the acceleration life model of high precision FOG. To this end, this paper carries out the following aspects of work: (1) The basic composition and main reliability index of high precision fiber optic gyroscope are introduced. (2) The sensitive stress of high-precision FOG is temperature and humidity. A high-precision FOG acceleration model based on temperature-humidity double-stress Peck model is established for the first time. (3) The life distribution model based on drift Brownian motion is analyzed, and the applicability of the life distribution model is determined by Monte Carlo simulation combined with the acceleration model of Peck model. (4) According to the performance degradation data of accelerated life test of FOG, the reliability of life distribution model of high precision FOG is evaluated.
On the base of an analyzing system, we demonstrate a testing method to reveal whether the FOG scale factor is stability after a long term ageing. The temperature of the chamber is set to 85°C in order to accelerate ageing of the adhesive. The FOG scale factor data is sampled each month. Results show that the MTTF (Mean Time to Failure) of the FOG coils is not satisfied with the application need. The analyzing system has good application prospects in testing the instabilities of the FOG’s Scale Factor.
The fiber optic gyroscope (FOG) has become to one of the most important sensors in developing due to light in quality, high accuracy, compact in dimension and long life. These features have developed new applications of the gyroscope not only in conventional aerospace application area but also in industrial aerospace, such as control and navigations of unmanned vehicles, antenna/camera stabilizers, and so on. Fiber coil is the core of fiber optic gyroscope. The accuracy of fiber optic gyroscope depends on the temperature performance of fiber coil.
In this paper, the temperature transient error model was built based on discrete mathematics model of SHUPE error in the Fiber optic gyroscope and the element physical model of the fiber coil. Based on the temperature distribution model mentioned above, the effects of the coil with different winding method and different geometric dimensions on the temperature performance of FOG were simulated under the same temperature condition. Theoretical analysis and experimental results showed by optimizing the design of the fiber coil, the temperature error of fiber coil can be reduced obviously.
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