| The fiber optic gyroscopes(FOGs)are widely used in fields of tactical missile,remote air defense missiles,air-to-air missile,ship,submarine and satelite for their advantages of all-solid state?high dynamic?low-cost?long lifetime?radiation tolerance.After many years of development,the high-precision FOGs have got increasingly mature,especially the key technology of fiber coil winding has been overcome,so the further development of high-precision FOG is possible.However,the FOGs are very sensitive to temperature fluctuation,especially fiber coil is worst affected by temperature.So handling with the influence of temperature disturbance well or not,will directly determine the measurement accuracy and stability of FOG.On this background,the thermal effect of fiber coil components is analyzed in detail by using finite element method(FEM)in this paper.And a more comprehensive thermally induced error model is developed to analyze the effect of temperature on interferometric fiber optic gyroscope(IFOG)more accurately.Moreover,this paper puts forward a new idea on the self compensating of IFOGs' temperature drift: the double fiber coil is only responsible for providing a spatial symmetric distribution on both sides of the fiber coils midpoint,and the heat-off spool just maintains a symmetric temperature distribution for the double fiber coils.The proposal of the concept provides a new idea for overcoming the temperature problem of the IFOG.Firstly,This paper introduces the research status of the influence of temperature on IFOG comprehensively,and focus on the analysis of the influence of temperature disturbance on the various parts of the IFOG.In addition,some currently feasible schemes about suppresssing temperature drift are shown.All the introductions above can lay the foundation for the subject research in its full swing and the key points to grasp.Next,based on the analysis of the mechanism of the temperature effect of IFOG,here propose to study the temperature effect of fiber coil as the starting point.Based on this,the temperature stability of IFOG can be improved by considering from three aspects: new fiber coil winding method,new-type fiber coil heat-off spool design and new polynomial compensation algorithm,and the overall research plan is given.Simulating the influence of temperature perturbations on the fiber coil accurately and establishing the exact relationship between the temperature of the IFOG and its thermal-induced errors are the two key points of this paper.In order to accurately simulate the temperature disturbance on the fiber coil,it is proposed that the finite element method can be used to analyze it.Based on this,the basic idea of finite element method and the basic heat transfer theory of fiber coil are analyzed,and the numerical solution of two-dimensional temperature field and equivalent thermal stress field of fiber coil is deduced.And then,in the case of the traditional two-dimensional “pure” Shupe thermal-induced error model,which is incomplete and does not consider thermal stress factor,a new two-dimensional thermal-induced error model and a three-dimensional thermal-induced error model are proposed.Considering the thermal and thermal stress factors,a late-model two-dimensional thermal-induced error model is deduced and the corresponding discretization expression is also given,which can more comprehensively describe the influence of temperature on the fiber coil section.In addition,considering the complexity of thermal disturbances,it is necessary to analyze the effect of local temperature perturbations on the fiber coil from the three-dimensional level.Based on this,Therefore,a three-dimensional thermal-induced error model is carried out and the corresponding discretization expression is also provided.According to the new thermal-induced error model,the influence of temperature on IFOG can be analyzed more accurately.In addition,this paper presents a new integrated scheme about fiber coil component: a new heat-off spool and its meshing with a double-cylinder(D-CYL)coil.Combining with the finite element method,the new thermal-induced error model and ANSYS software,the comparative simulation analysis was carried out and found that whether the quadrupole coil or cross coil,with the heat-off spool,both coils surface temperature can be homogenized effectively.So that the thermal drift errors of the fiber optic gyroscope can be restrained to a certain degree,especially the performance of the cross coil mesh with the heat-off spool is the best.In order to realize self compensating function of the fiber coil's temperature drift,a D-CYL fiber coil meshed with heat-off spool is proposed,and the performance of suppressing temperature drift can also be improved remarkably.Finally,a prototype of the D-CYL IFOG is built and the compensation effect is improved by introducing the upper and lower temperature gradient compensation coefficients when using the polynomial algorithm in the high-temperature and variable temperature stage for compensation.The normal temperature calibration tests,the basic temperature performance tests and the polynomial algorithm compensation tests are carried out for the D-CYL IFOG prototype.It is known that after compensating the D-CYL IFOG's,with 5 °C°/h heating and cooling rate,the zero drift can be controlled within 0.0571 °/h in the temperature range of 40 °C to 60 °C.In order to further solve the problem of suppressing temperature drift poorly in the high-temperature and variable temperature stage of the D-CYL IFOG,considering the simplified structural features of the fiber coil component,it is necessary to introduce the upper and lower temperature gradient factor for the polynomial compensation algorithm.After introducing the factor,the test results show that the D-CYL IFOG's ability of suppressing temperature drift has been further enhanced: the maximum zero-drift value can be reduced to 0.0345 °/h. |
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