• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A method comprising providing an optical input to an optical fiber interferometric gyroscope (GIFO) (110) at a first frequency and then at a second different frequency; detecting a difference in the GIFO (110) responses to the optical input at the first and second frequencies; and calculating a rotation speed as a function of the difference and a correction term.
    公开号:FR3027668A1
    申请号:FR1560086
    申请日:2015-10-22
    公开日:2016-04-29
    发明作者:Shaun M Detloff；James K Gingrich
    申请人:Boeing Co；
    IPC主号:
    专利说明:

    [0001] ROTATION SPEED CALCULATION FOR AN OPTICAL FIBEROMETRIC GYROSCOPE During the operation of an optical fiber interferometric gyro (GIFO), drift-related errors may occur over time. To correct drift-related errors, the GIFO scale factor can be recalibrated. During operation, an event may occur which degrades the performance of the GIFO. For example, an event causes the GIFO fiber optic coil to darken. To compensate for this degradation, the GIFO scale factor can be recalibrated. According to one embodiment of the present invention, a method comprises providing an optical input to an optical fiber interferometric gyroscope (GIFO) at a first frequency and then at a second different frequency; detecting a difference in GIFO responses to the optical input at the first and second frequencies; and calculating a rotation speed as a function of the difference and a correction term. In another aspect of the present invention, a system includes an optical fiber interferometric gyroscope (GIFO); an optical fiber light source for providing optical input to the GIFO at a first frequency and then at a second different frequency; a photodetector for detecting GIFO responses to the optical input at the first and second frequencies; and a processor for calculating a rotational speed based on a difference of the responses and a correction term. According to another embodiment of the present invention, a method for an optical fiber interferometric gyroscope (GIFO) comprises applying a known speed to the GIFO and determining the GIFO scale factors for the optical inputs to the first and second frequencies; providing an optical input to GIFO at the first frequency and detecting a first response of GIFO; switching the optical input to the second frequency and detecting a second response of the GIFO; and using a difference between the first and second responses, known velocity, and scale factors to determine a GIFO correction term. The correction term represents the sum of time-dependent errors in the first and second GIFO responses.
    [0002] These features and functions can be obtained independently in various embodiments or can be combined in other embodiments. Further details of the embodiments may be considered with reference to the following description and drawings.
    [0003] Figure 1 is an illustration of a system comprising an interferometric fiber optic gyroscope. Figure 2 is an illustration of a method of calculating a rotational speed in the interferometric fiber optic gyroscope. Figure 3 is an illustration of a time-dependent error estimation method during operation of the optical fiber interferometric gyroscope. Referring to FIG. 1, an optical fiber interferometric gyroscope system 100 comprises an optical fiber interferometric gyroscope (GIFO) 110. The GIFO 110 may comprise an optical fiber detection coil 112, an optical beam separation system 114, and a coupler 116. The system 100 further comprises a fiber light source 120, which provides an optical input to the GIFO 110. The optical beam splitting system 114 separates the optical input into two light beams which propagate in opposite directions through the sense coil 112. Upon return to the point of entry, these two inverse propagating light beams leave the sense coil 112, are recombined by the optical beam splitting system 114, and experience interference. When there is a rotation about an axis of the detection coil 112, the relative phases of the two outgoing beams, and therefore the position of their interference fringes, are shifted according to the angular velocity of the rotation. This is called a phase shift of Sagnac. The phase shift of Sagnac (0) can be expressed as Ei, where L and D are the length and the diameter of the sense coil 112, ^ ^, is the average wavelength of the light of the unladen source. , and n is the speed of rotation. The system 100 further comprises a photodetector 130 for detecting the phase shift of Sagnac. The photodetector 130 has an induced voltage which varies with the light intensity. An output signal (e.g., the induced voltage) of the photodetector 130 generally follows the cosine of the phase variation between the two beams output from the sense coil 112.
    [0004] The fiber light source 120 is configured to provide the optical input at a first frequency to the GIFO 110, and then switch to a second frequency. For example, the fiber light source 120 may include a first source for providing light at the first frequency, a second source for providing light at the second frequency, and an optical switch for switching the optical input between the first and the second frequencies. second sources. The photodetector 130 detects two different phase differences (GIFO responses). The system 100 further includes a processor 140 for calculating the rotational speed in response to an output of the photodetector 130. The processor 140 may also control the fiber light source 120 to switch the optical input between the first and second light sources. second frequencies. Another reference is to FIG. 2, which illustrates a method of using the system 100 to detect the rotational speed. At block 210, fiber light source 120 provides optical input to GIFO 110 at a first frequency, and then switches to a second, different frequency. Two different phase shifts of Sagnac are produced. The photodetector 130 detects these first and second responses of the GIFO 110. At the block 220, the processor 140 determines a difference in the GIFO responses to the optical input. The difference can be determined by measuring a difference in the voltages representing the first and second responses. At block 230, processor 140 calculates the rotational speed based on the difference and a correction term. An example of an equation for calculating the rotational speed is given below in Equation (4). The correction term is pre-calculated based on first and second predetermined scale factors at the first and second frequencies for the GIFO 110. For example, the scale factors and the correction term may be pre-calculated at the factory. before putting the GIFO 110 into service. During operation of GIFO 110, biases and first and second scale factors change over time. Contributing factors include changes in the input axis, fiber degradation, and temperature changes. For a conventional GIFO, these time-dependent errors should require recalibration. This is not the case for GIFO 110. As long as the offset in the first and second scale factors is about the same, the correction term will be stable, and the rotational speed can still be calculated based on the difference and the correction term. In other words, the function at block 230 can be repeated without having to recalibrate GIFO 110. During operation of GIFO 110, an event can occur which degrades the performance of GIFO 110. For example, an event causes blackening of GIFO 110. the detection coil 112. This event will cause the shift of the first and second scale factors in the same way. For a conventional GIFO, the event should result in a recalibration. This is not the case for the GIFO 110. The function at the block 230 can be repeated without having to recalibrate the GIFO 110. Reference is made to FIG. 3. A method for determining the correction term (C) is now be described. The system 100 can be used to determine its own correction term (C). At block 310, the first and second scale factors (s 2-1 and sF 2) for GIFO 110 are determined. A known speed can be applied to the GIFO 110, the fiber light source 120 provides an optical input to the GIFO 110 at a first or second frequency (fi or f2), the photodetector 130 measures the response of the GIFO, and the processor 140 uses a model to determine the scale factor (BPI or 5F2). For example, the scale factor can be derived from 0-20. At block 320, the fiber light source 120 provides an optical input to the GIFO 110 at the first frequency (f1), and the photodetector 130 detects the first GIFO response 110. Next, the fiber light source 120 switches the optical input to the second frequency (f2), and the photodetector 130 detects the second response of the GIFO 110. Thus, the photodetector 130 detects two phase shifts of 25 Sagnac different to the two different scale factors (s F1 and SF2). At block 330, processor 140 uses a difference between the first and second responses, known speed, and scale factors to determine the correction term (C) for GIFO 110. A model for calculating the correction term (C) can be derived as follows. 30 Consider the following model derived from IEEE Standard 952-1997 ("IEEE Standard Specification Format Guide and Test Procedure for Single-Axis Interferometric Fiber Optic Gyros", "Guide to IEEE Standard Specification Formats and Test Procedures for IEEE Standards". single-axis optical fiber interferometric gyroscopes "): (1) where sO is the scale factor, is the output response of GIFO 110, I is the optical input to GIFO 110 (° / h), E is the the environmental sensitivity of GIFO 110 (° / h), D is the drift rate (° / h), and rOe r is the scale factor error term. The term I can be rewritten as follows. ## EQU1 ## The term Df represents time dependent errors, which may include drift velocity (D) as well as other environmental sensitivities (E). Thus, the first and second responses to the optical input at the first and second frequencies f1 and f2 are presented in equations (2) and (3). (2) (3) Equation (4) expresses the known rotation speed (S2) with respect to the measured GIFO responses, the measured scale factors (5F1 and, and the correction term (C): (4) ) where DA_ + = C. The correction term (C) represents the sum of the time-dependent errors in the first and second GIFO responses The correction term (C) can be calculated from equation (4) .
    [0005] At block 340, processor 140 may store the correction term (C) for later use in calculating the rotational speed. Scale factors (SFi and 5F2) can be simplified to a constant value. For example, if (11 '-1 / 5 = 2, processor 140 can use equation (5) to calculate the rotation speed. (5) There is no minimum or maximum difference between the first and second frequencies, as long as the two frequencies can accurately measure the rotation speed, each frequency depends on the type of fiber, the phase modulation, the curvature of the coil, and the length of the coil. Frequencies may be infrared frequencies The system and method described herein are not limited to the above examples, for example, the fiber light source may provide light at more than two input frequencies. can be used to validate the calibration performed at the first and second frequencies.
    [0006] The GIFO 110 may have either an open loop or a closed loop configuration. GIFO 110 can be active or passive, multimode or singlemode, digital or analog. Typical applications for system 100 include monitoring, stabilization and inertial navigation systems.
    [0007] Although a system 100 comprising a single GIFO 110 has been described above, a system according to the invention is not limited. A multi-axial system may include a GIFO 110 for each axis. Each GIFO 110 can have its own correction term. Of course, the invention is not limited to the embodiments described above and shown, from which we can provide other modes and other embodiments, without departing from the scope of the invention. .
    权利要求:
    Claims (14)
    [0001]
    REVENDICATIONS1. A method comprising: providing an optical input to an optical fiber interferometric gyroscope (GIFO) (110) at a first frequency and then at a second different frequency; detecting a difference in the GIFO (110) responses to the optical input at the first and second frequencies; and calculating a rotation speed as a function of the difference and a correction term.
    [0002]
    The method of claim 1, wherein the correction term represents the sum of time-dependent errors in GIFO responses (110).
    [0003]
    The method of claim 1, wherein the rotational speed is not calculated based on a calibrated scale factor. 15
    [0004]
    The method of claim 1, wherein the correction term is pre-calculated based on the first and second initial scale factors corresponding to the first and second frequencies.
    [0005]
    The method of claim 4, further comprising continuing the repetition of the calculation of the rotational speed without calibration of the two scale factors if there are time-dependent errors or an event causing the offset of two scale factors in the same way.
    [0006]
    The method of claim 1, wherein the rotational speed (S2) is calculated by where SFi and SF2 are predetermined scale factors of the GIFO (110) corresponding to the first and second frequencies, C is the correction term. , and is the difference in the GIFO (110) responses to the optical input at the first and second frequencies.
    [0007]
    A system (100) comprising: an optical fiber interferometric gyroscope (GIFO) (110); an optical fiber light source (120) for providing an optical input to the GIFO (110) at a first frequency and then at a second different frequency; a photodetector (130) for detecting the GIFO (110) responses to the optical input at the first and second frequencies; and a processor (140) for calculating a rotational speed based on a difference of the responses and a correction term.
    [0008]
    The system (100) of claim 7, wherein the correction term represents the sum of time-dependent errors in GIFO responses (110).
    [0009]
    The system (100) of claim 7, wherein the rotational speed is not calculated based on a calibrated scale factor.
    [0010]
    The system (100) of claim 7, wherein the correction term is pre-calculated based on the first and second original scale factors at the first and second frequencies.
    [0011]
    The system (100) of claim 10, further comprising repeatedly calculating the rotational speed without calibration of the two scale factors if time-dependent errors occur or an event causing the shift. of the two scale factors in the same way.
    [0012]
    The system (100) according to claim 7, wherein the rotational speed (S2) is calculated by where SFi and SF2 are predetermined scale factors of the GIFO (110) corresponding to the first and second frequencies, C is the correction term, and is the difference in the GIFO (110) responses to the optical input at the first and second frequencies.
    [0013]
    A method for an optical fiber interferometric gyroscope (GIFO) (110) comprising: applying a known rate to the GIFO (110) and determining the GIFO scale factors (110) for the optical inputs to the first and second frequencies; providing an optical input to the GIFO (110) at the first frequency and detecting a first response of the GIFO (110); switching the optical input to the second frequency and detecting a second response of the GIFO (110); and using a difference between the first and second responses, known velocity, and scale factors to determine a correction term of the GIFO (110) representing the sum of time-dependent errors in the first and second GIFO responses (110).
    [0014]
    14. The method of claim 13, wherein the correction term (C) is calculated from where n is the known speed, SFi and SF2 are the scale factors corresponding to the first and second frequencies of the optical input, difference of the first and second responses of the GIFO (110).
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    2017-10-06| PLSC| Publication of the preliminary search report|Effective date: 20171006 |
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    优先权:
    申请号 | 申请日 | 专利标题
    US14522462|2014-10-23|
    US14/522,462|US10502585B2|2014-10-23|2014-10-23|Gyro rate computation for an interferometric fiber optic gyro|
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