JPH0560564A - Optical fiber gyroscope - Google Patents

Abstract

PURPOSE:To cover a wide dynamic range even without switching ranges at the frequency change of a sawtooth waveform signal concerning an optical fiber gyroscope and to maintain the sound linearity of gyroscope outputs and the stability of scale factors even with temperature changes. CONSTITUTION:An optical fiber gyroscope includes a signal processing portion 40 which outputs digital data D1 corresponding to the phase difference of light rays due to Sagnac effects, and circuit portions 52, 53 each of which digitally sets the frequency of a serrodyne modulating sawtooth waveform signal A15 and outputs a control signal A12 indicating the code of the data. The optical fiber gyroscope further includes sawtooth waveform signal generating portions 66, 68 each of which generates a digital sawtooth waveform corresponding signal D8 according to data on frequencies and generates an analogue sawtooth waveform corresponding signal P8 and a circuit portion 70 which generates gyroscope, outputs G1, G2 according to some 1 bit D8' of the digital sawtooth waveform corresponding signal P8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber gyro, and more particularly to a serrodyne modulation type closed loop optical fiber gyro having a wide dynamic range and outputting angular / angular velocity increments.

[0002]

2. Description of the Related Art FIG. 10 schematically shows a part of a structure of a serrodyne modulation type optical fiber gyro as a conventional example. In the figure, 10 is a light source, 12 and 18 are light distribution couplers, 14 is a polarizer, 16 is a crystal substrate having an electro-optic effect, 20 is a phase modulator, 22 is a serrodyne modulator, and 24 is perpendicular to the rotation axis. A loop formed by a wound polarization-maintaining single mode optical fiber, 26 is a light receiver, 30 is a signal generator, 40 is a signal processing device for an optical fiber gyro, 50a is a sawtooth wave signal frequency setting device, 60a Is a voltage controlled oscillation (VCO) type sawtooth wave signal generator, A1 is a phase modulator drive signal, A2 is a photoelectric conversion output signal, and A3 is a sawtooth wave signal. In this example, the sawtooth signal A3 is used as a drive signal for the serrodyne modulator 22 and forms a gyro output, that is, a rotational angular velocity output.

The optical distribution coupler 18, the phase modulator 20, and the serrodyne modulator 22 are, for example, lithium niobate (LiNbO ₃ ).
And an optical waveguide in which titanium (Ti) is diffused on the electro-optic crystal substrate 16 and means for changing the refractive index of the optical waveguide by applying a voltage to an electrode provided in the vicinity of the optical waveguide. There is. In the configuration of FIG. 10, the light beam emitted from the light source 10 is divided into two in the light distribution coupler 12, one of the two divided light beams is polarized by the polarizer 14, and only a certain polarized light is transmitted, This polarized beam is an optical splitter / coupler 18
Is split into two light beams at. One of the two divided light beams undergoes phase modulation of a constant frequency by the phase modulator 20, propagates in the counterclockwise direction through the optical fiber loop 24, and then is serrodyne modulated by the serrated signal by the serrodyne modulator 22. Then, the light is re-incident on the optical distribution coupler 18. Similarly, the other light beam split into two in the optical distribution coupler 18 undergoes serrodyne modulation by the serrodyne modulator 22, propagates in the clockwise direction in the optical fiber loop 24, and then is phase modulated by the phase modulator 20. Received,
It re-enters the light distribution coupler 18. The two light beams re-incident on the light splitting / combining unit 18 are combined, and the combined beam is transmitted by the polarizer 14 only in a certain polarized light. It is divided into two beams. One of the two divided light beams is guided to the photodetector 26 and propagates in the optical fiber loop 24 in opposite directions.
It is converted into an electric signal (photoelectric conversion output signal A2) corresponding to the interference light intensity depending on the phase difference between the two lights.

The phase modulator 20 is driven by a sine wave or square wave signal A1 having a constant frequency generated from the signal generator 30, and this signal A1 is also input to the signal processor 40. The signal processing device 40 synchronously detects the output (photoelectric conversion output signal A2) of the light receiver 26 in response to the signal A1 from the signal generating device 30 at a constant frequency. The output ΔV of the signal processing device 40 is expressed by the following equation.

ΔV = K · sin Δφ ………………………………………… (1) where Δφ is the phase difference between the two lights and K is a constant. Show. The sawtooth wave signal frequency setting device 50a has a function of integrating the output ΔV represented by the formula (1), and the VCO type sawtooth wave signal generator 60a has a function of integrating the output ΔV of the sawtooth wave signal frequency setting device 50a. An analog sawtooth signal A3 having a frequency corresponding to the magnitude of the output V is generated.

The phase difference Δφ is the phase difference φs of light due to the well-known Sagnac effect that occurs when a certain angular velocity is applied to the optical fiber loop 24 about an axis perpendicular to the loop, and the serrodyne modulator. 22 and the phase difference φm induced by it. The phase difference φs is represented by φs = 4πRLΩ / Cλ ………………………………………… (2), and the phase difference φm propagates in the opposite directions during serrodyne modulation. In order to make the discontinuous portion of the phase difference Δφ caused by the propagation delay of two lights continuous by using the periodicity of the output related to the phase difference, the condition that the phase amount amplitude by the sawtooth signal is set to 2π Below, φm = 2πτ / Tm = 2πnLfm / C ………………………… (3) Where R is the radius of the optical fiber loop 24,
L is the length of the optical fiber forming the optical fiber loop 24,
Ω is the input rotation angular velocity, C is the speed of light in vacuum, λ is the wavelength of light in vacuum, τ is the time required for light to propagate through the optical fiber loop 24, Tm is the period of the sawtooth signal A3, and n is The index of refraction of the optical fibers forming the optical fiber loop 24, and fm, indicate the frequency of the sawtooth signal A3.

In the serrodyne modulation type optical fiber gyro, when the input rotation angular velocity Ω changes, the output ΔV of the signal processing device 40 is integrated by the sawtooth wave signal frequency setting device 50a so as to be a negative feedback. Applied to the linear wave signal generator 60a, and the phase difference Δ
The control is performed so that φ (that is, the output ΔV of the signal processing device 40) is always maintained at a predetermined value (usually 0).
Therefore, if Δφ = φs + φm = 0, then from equations (2) and (3), Ω = nλfm / 2R …………………………………………………… (4) The input rotational angular velocity over a wide dynamic range can be detected by counting the frequencies of the sawtooth wave signal.

When the gyro output is a pulse train having a frequency equal to the frequency of the sawtooth wave signal A3, one pulse is an angle increment pulse output having a constant angle Δθ as a weight. However, Δθ is expressed by the equation (4) as follows: Δθ = Ω / fm = nλ / 2R …………………………………… (5).

[0009]

In the above-mentioned conventional serrodyne modulation type closed-loop optical fiber gyro, the sawtooth wave signal applied to the serrodyne modulator 22 is used.
Since A3 is generated by the analog VCO type sawtooth wave signal generator 60a, there is a disadvantage that the variable range of the generated frequency is limited.

Therefore, in order to obtain a wide dynamic range of the order of 10 ⁶ which is often required, the switching must be performed by using a plurality of sawtooth wave signal generators each having a different frequency range. It was necessary to correct the discontinuity in the boundary region, and its control was extremely complicated. Further, the amplitude of the sawtooth wave signal is likely to fluctuate due to temperature changes and the like, which causes a problem that the linearity of the gyro output and the stability of the scale factor are deteriorated.

The present invention has been made in view of the above problems in the prior art, and covers a wide dynamic range without changing the range when the frequency of the sawtooth wave signal changes, and even when there is a change in temperature. An object of the present invention is to provide an optical fiber gyro which can maintain good linearity of gyro output and stability of scale factor.

[0012]

In order to solve the above-mentioned problems, according to the first embodiment of the present invention, light is simultaneously propagated in mutually opposite directions in an optical fiber loop which cooperates with a rotation axis,
The light propagating in both directions is subjected to phase modulation with a signal of a constant frequency, and serrodyne modulation is performed with an analog sawtooth wave signal of a variable frequency, and the interfering light of the modulated bidirectional light is detected and its light intensity is detected. An optical system that outputs a photoelectric conversion output signal according to, and extract a component synchronized with the signal of the constant frequency from the output photoelectric conversion output signal,
A signal processing unit that outputs digital error data corresponding to the phase difference of the lights propagating in opposite directions, and a multiplication unit that multiplies the output error data by digital data that indicates a coefficient that determines a feedback loop gain. And adding the previous sawtooth wave signal frequency setting data to the output data of the multiplying means to set and output new sawtooth wave signal frequency setting data, and to output the set sawtooth wave signal frequency setting data. Adder means for outputting a control signal for indicating a sign, counter means for incrementing / decrementing the contents when the adder means overflows to generate a digital sawtooth wave corresponding signal, and digital sawtooth wave corresponding signal And a D / A converter for converting the analog sawtooth wave signal to the analog output signal Optical fiber gyro, characterized in that in response to any bit with the control signal of the sawtooth wave corresponding signal and a gyro output generator for generating an gyro output is provided.

Further, according to the second aspect of the present invention, light is simultaneously propagated in opposite directions in the optical fiber loop cooperating with the rotation axis, and a phase of a signal having a constant frequency is applied to the light propagated in both directions. An optical system that performs modulation and performs serrodyne modulation with an analog sawtooth wave signal of variable frequency, detects the interference light of the modulated light in both directions, and outputs a photoelectric conversion output signal according to the light intensity, A signal processing unit that extracts a component synchronized with the signal of the constant frequency from the output photoelectric conversion output signal and outputs digital error data according to the phase difference of the lights propagating in opposite directions, and the output. Multiplying means for multiplying the error data thus obtained by digital data indicating a coefficient for determining the feedback loop gain, and output data of the multiplying means, the sawtooth wave signal frequency setting of the last time. First addition means for adding data to set and output new sawtooth wave signal frequency setting data, and outputting a control signal for instructing the sign of the set sawtooth wave signal frequency setting data; Second addition means for adding the previous addition data to the sawtooth wave signal frequency setting data output from the first addition means, and outputting a carry signal when an overflow occurs, and a second addition means for outputting the carry signal. Counter means for incrementing / decrementing a number to generate a digital sawtooth wave corresponding signal; a D / A converter for converting the digital sawtooth wave corresponding signal to the analog sawtooth wave signal; A gyro output generation unit that generates a gyro output in response to the control signal and the carry signal output from the second adding means is provided. Optical fiber gyro according to is provided.

Furthermore, according to the third aspect of the present invention, light is simultaneously propagated in opposite directions to each other in the optical fiber loop cooperating with the rotation axis, and the light propagated in both directions is phased by a signal of a constant frequency. An optical system that performs modulation and performs serrodyne modulation with an analog sawtooth wave signal of variable frequency, detects the interference light of the modulated light in both directions, and outputs a photoelectric conversion output signal according to the light intensity, A signal processing unit that extracts a component synchronized with the signal of the constant frequency from the output photoelectric conversion output signal and outputs digital error data according to the phase difference of the lights propagating in opposite directions, and the output. A sawtooth wave signal frequency setting section for digitally setting the frequency of the serrated wave modulation sawtooth wave signal based on the error data obtained; and the digitally set frequency data And a gyro output for generating a gyro output based on the digitally set sawtooth wave signal frequency setting data, and a direct synthesis digital synthesizer type sawtooth wave signal generator for generating the analog sawtooth wave signal based on An optical fiber gyro is provided that includes a generator.

[0015]

According to the configuration of the first embodiment, since the sawtooth wave signal generating section is constructed by the direct synthesis digital synthesizer system to form the closed loop, the range is not changed when the frequency of the analog sawtooth wave signal is changed. The dynamic range can be expanded and the amplitude of the analog sawtooth wave signal is controlled to be stable, so even if there is a change in temperature, the linearity of the gyro output can be maintained well and the scale It becomes possible to maintain the stability of the factor.

Since any one bit of the digital sawtooth wave corresponding signal transits at the frequency corresponding to the input angular velocity, one cycle thereof indicates an angular increment. Therefore, if any one bit of this data is input to the gyro output generation unit together with the control signal and appropriately processed, a digital angle output and an analog angle output can be obtained. this is,
For example, it can be used for a host computer, a servomotor, etc. for navigation calculation.

Details of other structural features and operations of the present invention, including the second and third embodiments, will be described using the embodiments described below with reference to the accompanying drawings.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of the main part of a serrodyne modulation type optical fiber gyro as an embodiment of the present invention.
FIG. 2 schematically shows a part of the structure of the optical system of the optical fiber gyroscope in each of the embodiments including the embodiment of FIG. The configurations of the signal generator 30 and the signal processor 40 shown in FIG. 1 and the optical system shown in FIG. 2 are the same as those of each element shown in FIG.

In FIG. 1, 50 is a sawtooth wave signal frequency setting device, 60 is a sawtooth wave signal generator of the direct synthesis digital synthesizer system, and 70 is a gyro output generating circuit. The sawtooth wave signal frequency setting device 50 is a digital multiplication means 52 responsive to the digital error data D1 output from the optical fiber gyro signal processing device 40 and the digital data D2 instructing the coefficient for determining the feedback loop gain. An adding means 54 for adding the output data D3 of the digital multiplying means to the previous sawtooth wave signal frequency setting data D5, and a new sawtooth wave signal frequency setting data D4 output from the adding means from an external clock. And a latching means 56 for latching based on the signal A11.

The sawtooth wave signal generator 60 adds the sawtooth wave signal frequency setting data D4 output from the sawtooth wave signal frequency setting device 50 to the previous addition data D6.
And a latch means 64 for latching the addition data D7 output from the addition means based on an external clock signal A14.
And an up / down counter for counting a carry (carry signal A13) caused by the overflow of the adding means 62 in response to the up / down switching signal A12 output from the adding means 54 in the sawtooth wave signal frequency setting device 50.
66 and a D / A converter 68 for converting the digital sawtooth wave corresponding signal D8 output from the counter into an analog sawtooth wave signal (serodyne modulator drive signal) A15. Where the up / down switching signal
A12 is a signal that identifies the sign of the sawtooth signal,
The sign data indicating positive / negative rotation of the sawtooth wave signal frequency setting data D4 is shown, and the carry signal A13 is
The signal corresponding to the frequency of the sawtooth wave signal is shown.

Further, the gyro output generation circuit 70 converts any one bit (denoted as D8 ') of the digital sawtooth wave corresponding signal D8 into the code data (up / down switching signal A1).
2) Counting and output the result as a gyro output (digital angle output G1) as an up / down counter 71, and the counter output is digital-to-analog converted to a gyro output (analog angle output G2). ) Is generated by the D / A converter 72.

In the optical fiber gyro configured as described above, the output (photoelectric conversion output signal A2) of the photodetector 26 corresponding to the interference light intensity is output by the signal processing device 40 for the optical fiber gyro (for example, Japanese Patent Application No. No. 121236) digitally demodulated by the signal generator 30
A component synchronized with the fundamental wave component (A1) of the output signal of is detected. The component detected in this way is input to the sawtooth wave signal frequency setting device 50 as error data D1.

In the sawtooth wave signal frequency setting device 50,
The digital multiplication means 52 multiplies the error data D1 by the coefficient (D2) that determines the feedback loop gain, and outputs the digital control amount D3. The adding means 54 adds the previous sawtooth wave signal frequency setting data D5 to the digital control amount D3 and outputs new sawtooth wave signal frequency setting data D4. The latch means 56 latches the new sawtooth wave signal frequency setting data D4 for one clock in synchronization with the clock signal A11 from the outside, and outputs the previous sawtooth wave signal frequency setting data.
D5 is output to the adding means 54. The new sawtooth wave signal frequency setting data D4 generated in this way is directly input to the sawtooth wave signal generator 60 of the direct synthesis digital synthesizer system.

In the sawtooth wave signal generator 60 of the direct synthesis digital synthesizer system, the adding means 62 includes new sawtooth wave signal frequency setting data D4 and previous addition data D6.
Is added, new addition data D7 is output, and a carry signal A13 is output when the operation result overflows and a carry occurs. The latch means 64 latches the new addition data D7 for one clock in synchronization with the clock signal A14 from the outside, and outputs the previous addition data D6 to the addition means 62. The up / down counter 66 increments / decrements the number of carry signals A13 based on the up / down switching signal A12 representing the sign of the new sawtooth wave signal frequency setting data D4, counts, and digitally counts based on the counted number. A sawtooth wave corresponding signal D8 is output.
The D / A converter 68 is a digital sawtooth wave compatible signal.
Convert D8 into an analog sawtooth signal A15. The analog sawtooth wave signal A15 is input to the serrodyne modulator 22 and used as a drive signal for serrodyne modulation.

In the above configuration, by setting the number of bits of the sawtooth wave signal frequency setting data D4, D5 and the addition data D6, D7 large, the value of the new sawtooth wave signal frequency setting data D4 becomes small. When the value of the new sawtooth wave signal frequency setting data D4 increases in a long cycle, the carry signal A13 is output from the adding means 62 in a short cycle. The up / down counter 66 increments or decrements the number of carry signals A13 to count, and the count value is counted by the D / A converter 68.
If it is converted into an analog signal via the, a sawtooth wave signal A15 having a short period to a long period can be generated. Therefore, serrodyne modulation in a wide frequency range becomes possible, and the dynamic range as an optical fiber gyro can be expanded.

Further, the time for converting the frequency is determined by the latch means.
56 clock signal A11 and latch means 64 clock signal A1
Since it depends on 4, it is possible to change the frequency (cycle) of the analog sawtooth wave signal A15 at high speed by using the clock signals A11 and A14 at a high frequency, and to improve the output frequency characteristics of the optical fiber gyro. Can be raised to frequency. Therefore, even when the frequency of the sawtooth wave signal A15 changes due to a change in temperature or the like, the linearity of the gyro output can be maintained well and the stability of the scale factor can be maintained.

Further, a digital sawtooth wave corresponding signal D8
Since an arbitrary bit D8 'of the signal transitions at a frequency corresponding to the input angular velocity, one cycle thereof indicates an angular increment as shown in the above-mentioned equation (5). Therefore, as shown in FIG. 1, if any one bit D8 'of this data D8 is input to the up / down counter 71 together with the sign data (up / down switching signal A12) indicating the positive or negative rotation of the data D8. ,
A digital angle output G1 is obtained and can be used in the host computer for navigation calculation. In addition, the output of the counter 71 is passed through the D / A converter 72 to a digital / digital converter.
If you do analog conversion, you can get analog angle output G2,
It can be used to control a servomotor or the like.

Generally, in a signal processing apparatus which is digitally calculated, its output is discontinuous during updating of data, but in the method of the present embodiment described above, a linearly interpolated angle output can be obtained. it can. FIG. 3 shows the configuration of the main part (gyro output generation circuit 70a) in a modification of the above embodiment.

The gyro output generation circuit 70a shown in the figure outputs an interval timer 81 for generating a timing signal TS at an arbitrary time interval and an arbitrary 1 bit D8 'of a digital sawtooth wave corresponding signal D8 as code data (up / up). The up / down counter 82 that counts in response to the down switching signal A12) and clears the count value by the timing signal TS, and the output of the counter is a timing signal.
Latch circuit 83 that latches in response to TS and outputs the result as a gyro output (digital angular velocity output G3)
And a D / A converter 84 for digital / analog converting the output of the latch circuit to generate a gyro output (analog angular velocity output G4).

An arbitrary bit D8 'of the digital sawtooth wave corresponding signal D8 transits at a frequency corresponding to the input angular velocity, but its response depends on the clock signal A11 in the sawtooth signal frequency setting device 50. In this case, since the output frequency is constant between the clock signals, the output is time-averaged and the angle increases. Therefore, in the embodiment of FIG. 3, if the output of the up / down counter 82 is cleared to 0 at any interval by the timing signal TS from the interval timer 81, the averaged output during that interval, that is, the digital angular velocity output. G3 is obtained and can be used in the host computer for navigation calculation. Further, if the digital angular velocity output G3 is digital / analog converted through the D / A converter 84, an analog angular velocity output G4 can be obtained.

FIG. 4 shows the configuration of the main part (gyro output generation circuit 70b) in another modification. The illustrated gyro output generation circuit 70b is the gyro output generation circuit 70 of FIG.
And a gyro output generation circuit 70a shown in FIG. In other words, two up / down counters
Angle outputs G1, G2 and angular velocity outputs G3, G4 using 71 and 82
I try to get both of them at the same time.

FIG. 5 shows the configuration of the main part of the second embodiment of the present invention. Signal generator 30 and signal processor shown in FIG.
The configurations of 40, the saw-tooth wave signal frequency setting device 50, and the saw-tooth wave signal generator 60 are the same as those of the embodiment of FIG. The gyro output generation circuit 70c in FIG. 5 is the addition means 62 of the sawtooth wave signal generation device 60.
The carry signal A13 output from is counted in response to the code data (up / down switching signal A12),
An up / down counter 75 that outputs the result as a gyro output (digital angle output G1), and a D / A converter that digitally / analog converts the output of the counter to generate a gyro output (analog angle output G2).
And 76.

In this case, since the carry signal A13 transits at the frequency corresponding to the input angular velocity, one cycle of the carry signal A13 is expressed by the equation (5).
Indicates the angular increment as shown in. Therefore, as shown in FIG. 5, the carry signal A13 is input to the up / down counter 75 together with the sign data (up / down switching signal A12) indicating positive or negative rotation of the digital sawtooth wave signal frequency setting data D4. For example, a digital angle output G1 can be obtained and used in a host computer for navigation calculation. Also, the output of the counter 75 is D / A
If digital / analog conversion is performed through the converter 76, an analog angle output G2 can be obtained and used for controlling the servomotor or the like.

Also in this embodiment, a linearly interpolated angle output can be obtained as in the embodiment of FIG. FIG. 6 shows the configuration of the main part (gyro output generation circuit 70d) in a modification of the embodiment of FIG. The gyro output generation circuit 70d shown in FIG.
Interval timer 85 for generating the carry signal A1
3 is counted in response to code data (up / down switching signal A12), and the up / down counter 86 that clears the count value by the timing signal TS1 and the output of the counter in response to the timing signal TS1 A latch circuit 87 for latching and outputting the result as a gyro output (digital angular velocity output G3), and a D / A for digital / analog converting the output of the latch circuit to generate a gyro output (analog angular velocity output G4) And a converter 88.

The carry signal A13 transits at a frequency corresponding to the input angular velocity, but its responsiveness depends on the clock signal A11 in the sawtooth wave signal frequency setting device 50. In this case, since the output frequency is constant between the clock signals, the output is time-averaged and the angle increases. Therefore, in the embodiment of FIG. 6, the up / down counter 86
Of the timing signal from the interval timer 85
If you clear to 0 at any interval by TS1,
The averaged output over that interval, ie the digital angular velocity output G3, is available and available on the host computer for the navigation calculation. In addition, the digital angular velocity output G3 is passed through the D / A converter 88 to digital /
An analog angular velocity output G4 is obtained by analog conversion.

FIG. 7 shows the configuration of the main part (gyro output generation circuit 70e) in another modification. The illustrated gyro output generation circuit 70e is the gyro output generation circuit 70 of FIG.
c and a gyro output generation circuit 70d shown in FIG. That is, by using the two up / down counters 75 and 86, the angle outputs G1 and G2 and the angular velocity outputs G3 and G
I try to get both 4 at the same time.

FIG. 8 shows the structure of the main part of the third embodiment of the present invention. As in the case of FIG. 5, the configurations of the signal generator 30, the signal processor 40, the sawtooth wave signal frequency setting device 50 and the sawtooth wave signal generator 60 are the same as those of the embodiment of FIG. The description is omitted. The gyro output generation circuit 70f in FIG. 8 includes a D / A converter 91 for digital / analog converting the digital frequency setting data D4 output from the sawtooth wave signal frequency setting device 50,
An integrator that integrates the output of the D / A converter and outputs the result as a gyro output (analog angle output G2)
Have 92 and. In this embodiment, since the digital sawtooth wave signal frequency setting data D4 indicates the input angular velocity, that is, the gyro output (digital angular velocity output G3), this data is taken into the host computer and used for navigation calculation. be able to. Further, if this data output G3 is digital-to-analog converted through the D / A converter 91 and further integrated by the integrator 92, an analog angle output G2 can be obtained and can be used for control of the servomotor and the like.

FIG. 9 shows the configuration of the main part (gyro output generation circuit 70g) in a modification of the embodiment shown in FIG.
The gyro output generation circuit 70g shown in the figure accumulates the digital frequency setting data D4 output from the sawtooth wave signal frequency setting device 50 in synchronization with the clock signal A11, and outputs the result to the gyro output (digital angle output G1 ), And a D / A converter 98 for digital / analog converting the output G1 of the accumulator to generate a gyro output (analog angle output G2). Accumulator 95
Is an addition means 96 for adding the digital sawtooth wave signal frequency setting data D4 to the previous addition data (digital angle output G1), and the addition data D9 output from the addition means.
Is latched in response to the clock signal A11 and is output as a digital angle output G1.

In the present embodiment, the output of the sawtooth wave signal frequency setting device 50, that is, the digital sawtooth wave signal frequency setting data D4 is the input angular velocity updated at a cycle synchronized with the clock signal A11 in the setting device. Therefore, if this data is accumulated in synchronization with the clock signal A11, a digital angle output G1 can be obtained. This can be loaded into a host computer and used for navigation calculation, attitude control, etc. Also, this data output
If G1 is digital-to-analog converted through the D / A converter 98, an analog angle output G2 can be obtained and used for controlling the servomotor or the like.

[0040]

As described above, according to the present invention, the sawtooth wave signal generator is directly combined into a digital synthesizer to form a closed loop, so that the dynamic range can be expanded without switching the range. You can In addition, since the amplitude of the sawtooth wave signal is controlled to be stable, it is possible to maintain good linearity of the gyro output and improve the stability of the scale factor even when there is a change in temperature. it can.

Furthermore, it is possible to reduce the weight per pulse of the angle increment pulse, thereby increasing the minimum resolution.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a serrodyne modulation type optical fiber gyro as a first embodiment of the present invention.

FIG. 2 is a block diagram schematically showing a part of the configuration of the optical system of the optical fiber gyroscope in each embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a main part in a modification of the embodiment of FIG.

FIG. 4 is a block diagram showing a configuration of a main part in another modification of the embodiment of FIG.

FIG. 5 is a block diagram showing a configuration of a main part of a serrodyne modulation optical fiber gyro as a second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a main part in a modification of the embodiment in FIG.

FIG. 7 is a block diagram showing a configuration of a main part in another modification of the embodiment of FIG.

FIG. 8 is a block diagram showing a configuration of a main part of a serrodyne modulation optical fiber gyro as a third embodiment of the present invention.

9 is a block diagram showing a configuration of a main part in a modification of the embodiment in FIG.

FIG. 10 is a block diagram schematically showing a part of a configuration of a serrodyne modulation type optical fiber gyro as an example of a conventional type.

[Explanation of symbols]

24 ... Optical fiber loop 40 ... Signal processing device 50 ... Sawtooth wave signal frequency setting device 52 ... Multiplier means 54, 62 ... Addition means 56, 64 ... Latch means 60 ... Sawtooth wave signal generator 66, 71, 75, 82 , 86… Counter means (up / down counter) 68,72,76,84,88,91,98… D / A converter 70,70a to 70g… Gyro output generation circuit 81,85… Timer 83,87… Latch means 92 ... Integrator 95 ... Accumulator A1 ... Constant frequency signal (phase modulation signal) A2 ... Photoelectric conversion output signal A11, A14 ... Clock signal A12 ... Control signal (up / down switching signal) A13 ... Carry signal A15 ... Variable Frequency analog sawtooth wave signal (serodyne modulation signal) D1 ... Signal according to the phase difference of light due to Sagnac effect (error data) D2 ... Data instructing coefficient to determine feedback loop gain D3 ... Digital control amount D4 ... New sawtooth signal frequency setting Data D5 ... Previous sawtooth wave signal frequency setting data D6 ... Previous addition data D7 ... New addition data D8 ... Digital sawtooth wave corresponding signal D8 '... Arbitrary 1 bit of digital sawtooth wave corresponding signal G1 ~ G4 ... Gyro output TS, TS1 ... Timing signal

Claims (11)

[Claims] 1. An optical fiber loop (24) cooperating with a rotation axis.
Light is propagated in opposite directions at the same time, phase modulation is performed on the light propagating in both directions by a constant frequency signal (A1), and serrodyne modulation is performed by a variable frequency analog sawtooth wave signal (A15). A photoelectric conversion output signal that detects the modulated interference light of both directions and that corresponds to the light intensity
(A2) output optical system, and the digital error data corresponding to the phase difference of the light propagating in the opposite directions by extracting a component synchronized with the signal of the constant frequency from the output photoelectric conversion output signal A signal processing section (40) for outputting (D1), multiplication means (52) for multiplying the output error data by digital data (D2) indicating a coefficient for determining a feedback loop gain, and a multiplication means (52) for the multiplication means. Add the previous sawtooth wave signal frequency setting data (D5) to the output data (D3) to set and output new sawtooth wave signal frequency setting data (D4), and set the sawtooth wave signal frequency. Addition means (54) that outputs a control signal (A12) that indicates the sign of the setting data, and increments / decrements the content when the addition means overflows to generate a digital sawtooth wave corresponding signal (D8) counter A step (66), a D / A converter (68) for converting the digital sawtooth wave corresponding signal into the analog sawtooth wave signal (A15), and a digital sawtooth wave output from the adding means. Gyro output generation unit for generating gyro output (G1 to G4) in response to any one bit (D8 ') of the signal and the control signal
(70, 70a, 70b), and an optical fiber gyro characterized by the above-mentioned. 2. The gyro output generation unit (70) increments / decrements by the control signal in response to an arbitrary 1-bit transition of the digital sawtooth wave corresponding signal, and outputs a digital angle output (G1). And a D / A converter (7) for D / A converting the digital angle output to generate an analog angle output (G2).
2. The optical fiber gyro according to claim 1, further comprising 2). 3. The gyro output generator (70a) includes a timer (81) for generating a timing signal (TS) at an arbitrary time interval.
A counter means (82) for counting any one bit of the digital sawtooth wave corresponding signal by the control signal and clearing the count value by the timing signal; and an output of the counter means for the timing signal. Latches in response to a digital angular velocity output
A latch means (83) for generating (G3) and a D / A converter (84) for D / A converting the digital angular velocity output to generate an analog angular velocity output (G4). The optical fiber gyro according to claim 1. 4. The gyro output generator (70b) is configured by a combination of the gyro output generator (70) according to claim 2 and the gyro output generator (70a) according to claim 3. The optical fiber gyro according to claim 1, which is characterized in that. 5. An optical fiber loop (24) cooperating with a rotation axis.
Light is propagated in opposite directions at the same time, phase modulation is performed on the light propagating in both directions by a constant frequency signal (A1), and serrodyne modulation is performed by a variable frequency analog sawtooth wave signal (A15). A photoelectric conversion output signal that detects the modulated interference light of both directions and that corresponds to the light intensity
(A2) output optical system, and the digital error data corresponding to the phase difference of the light propagating in the opposite directions by extracting a component synchronized with the signal of the constant frequency from the output photoelectric conversion output signal A signal processing section (40) for outputting (D1), multiplication means (52) for multiplying the output error data by digital data (D2) indicating a coefficient for determining a feedback loop gain, and a multiplication means (52) for the multiplication means. Add the previous sawtooth wave signal frequency setting data (D5) to the output data (D3) to set and output new sawtooth wave signal frequency setting data (D4), and set the sawtooth wave signal frequency. First adding means (54) for outputting a control signal (A12) for instructing the sign of the setting data, and previous addition data (D6) for the sawtooth wave signal frequency setting data output from the first adding means. And an overflow occurred Second adder means (62) for outputting a carry signal (A13) and counter means (66) for incrementing / decrementing the number of output carry signals to generate a digital sawtooth wave corresponding signal (D8). ), A D / A converter (68) for converting the digital sawtooth wave corresponding signal to the analog sawtooth wave signal (A15), and a control signal output from the first and second adding means. An optical fiber gyro, comprising: a gyro output generation unit (70c, 70d, 70e) that generates gyro outputs (G1 to G4) in response to a carry signal. 6. The gyro output generator (70c) includes counter means (75) for incrementing / decrementing the carry signal by the control signal to generate a digital angle output (G1), and the digital angle output. 6. The fiber optic gyro according to claim 5, further comprising a D / A converter (76) for D / A converting the analog angle output (G2). 7. The gyro output generator (70d) includes a timer (8) for generating a timing signal (TS1) at an arbitrary time interval.
5), counter means for counting the carry signal by the control signal and clearing the count value by the timing signal (86), and latching the output of the counter means in response to the timing signal, Latch means (87) for generating digital angular velocity output (G3)
6. The optical fiber gyro according to claim 5, further comprising: a D / A converter (88) for D / A converting the digital angular velocity output to generate an analog angular velocity output (G4). 8. The gyro output generation unit (70e) is configured by a combination of the gyro output generation unit (70c) according to claim 6 and the gyro output generation unit (70d) according to claim 7. The optical fiber gyro according to claim 5, which is characterized in that. 9. An optical fiber loop (24) cooperating with a rotation axis.
Light is propagated in opposite directions at the same time, phase modulation is performed on the light propagating in both directions by a constant frequency signal (A1), and serrodyne modulation is performed by a variable frequency analog sawtooth wave signal (A15). A photoelectric conversion output signal that detects the modulated interference light of both directions and that corresponds to the light intensity
(A2) output optical system, and the digital error data corresponding to the phase difference of the light propagating in the opposite directions by extracting a component synchronized with the signal of the constant frequency from the output photoelectric conversion output signal A signal processing section (40) for outputting (D1), and a sawtooth wave signal frequency setting section (50) for digitally setting the frequency of the serrated wave modulation sawtooth wave signal based on the output error data. A sawtooth wave signal generator (6) of a direct synthesis digital synthesizer for generating the analog sawtooth wave signal (A15) based on the digitally set frequency data (D4)
0), and a gyro output generation unit (70f, 70g) for generating a gyro output (G1 to G3) based on the digitally set sawtooth wave signal frequency setting data. gyro. 10. The gyro output generation unit (70f) outputs the digitally set sawtooth wave signal frequency setting data as a digital angular velocity output (G3), and outputs the sawtooth wave signal frequency setting data. D / A converter (91) for performing D / A conversion of the signal and an integrator (92) for integrating the output of the D / A converter to generate an analog angle output (G2)
The optical fiber gyro according to claim 9, further comprising: 11. The gyro output generator (70g) synchronizes the digitally set sawtooth wave signal frequency setting data with a clock signal (A11) used in the sawtooth wave signal frequency setting unit. Accumulate and digital angle output
An accumulator (95) for generating (G1) and D for D / A converting the digital angle output to generate an analog angle output (G2).
The optical fiber gyro according to claim 9, further comprising an A / A converter (98).