JPH0447215A - Optical rotation angular velocity sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical rotational angular velocity sensor, particularly a phase modulation type optical rotational angular velocity sensor.

[Prior Art] The configuration of a phase modulation type optical rotation angular velocity sensor will be described with reference to FIG.

The optical system includes a laser light source 1. Polarizer 31 Phase modulator 4. Sensing Group 5. Photoreceiver6. Preamplifier 7, each 1
and two optical couplers 2a.

2b.

The light from the laser beam if is split by an optical coupler 2a, one of which is split by a polarizer 3. Sensing Blue 15 via optical coupler 2b
guided by. The left and right light propagated through the sensing loop 5 is recombined by the optical coupler 2b, and the polarizer 3. The light is guided to a light receiver 6 via an optical coupler 2a. Sensin Group 5
When rotates at an angular velocity Ω, a phase difference occurs between the left and right light propagating through the sensing loop 5 (Sagnac effect).
, the light output reaching the light receiver 6 changes. The detection signal from the light receiver 6 is input to the signal processing circuit 12 via the preamplifier 7.

Specifically, the signal processing circuit 12 includes a synchronous detection circuit 8, an A/
D converter9. CPU10. A sine wave fr+ of a constant frequency is applied from the oscillator 11 to the 0-phase modulator 4 each consisting of one oscillator 11°, and the clockwise and counterclockwise lights of the sensing loop 5 are phase-modulated at this frequency. As a result, the optical receiver 6 outputs the phase modulation frequency and its harmonic components. Each frequency component is separated by a synchronous detection circuit 8, converted into a digital signal by an A/D converter 9, and then converted to a digital signal by an A/D converter 9.
The angular velocity Ω is calculated by PU10.

By the way, in the calculation of this angular velocity, the degree of phase modulation (
The degree of phase bias applied to both the left and right beams is used, and is usually set as a constant. In order to make this calculation possible, it is necessary to make the degree of phase modulation constant.

Therefore, in general, the voltage width of the sine wave f11 of a constant frequency applied from the oscillator 11 to the phase modulator 4 is controlled, and the degree of modulation of the phase modulator 4 is thereby adjusted to manage the scaling of the rotational angular velocity. are doing.

[8 Problems to be Solved by the Invention] However, in the conventional optical rotational angular velocity sensor, an operation for controlling the phase modulator 4 is required as described above. For this reason, a circuit dedicated to control is required, which increases the circuit scale and makes it expensive, and since the number of elements increases, assembly becomes complicated, resulting in lower reliability.

Furthermore, since the timing of signal detection and the timing of modulation degree control are shifted by one cycle, the degree of phase modulation is likely to be different from a constant value, resulting in a measurement error.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a high-performance optical rotational angular velocity sensor that can be configured with a small-scale circuit.

[Means for Solving the Problems] The present invention splits light from a light source with an optical power grapher, shifts the phase of the branched lights with a phase modulator, guides them to a sensing loop, and propagates the left and right lights through the sensing loop. In a phase modulation type optical rotation angular velocity sensor, the two-way light is recombined with optical power 1 and detected by the receiver, and the signal processing circuit obtains angular velocity information.The degree of phase modulation is determined from the output of a harmonic signal with respect to the phase modulation frequency This configuration is provided with calculation means for calculating the angular velocity using the obtained phase modulation degree.

Preferably, the calculation means is configured to obtain the degree of phase modulation from the ratio of the second harmonic signal and the fourth harmonic signal with respect to the phase modulation frequency.

5. Effect] Since the degree of phase modulation is determined from the output of the harmonic signal with respect to the phase modulation frequency, and the angular velocity is calculated using that value, there is no need to control the degree of modulation of the phase modulator, and the circuit scale can be significantly reduced. can be made smaller.

[Example 7] Examples of the optical rotation angular velocity sensor of the present invention will be described below.

The configuration of the optical rotation angular velocity sensor is basically the same as that shown in FIG.
Phase modulation is applied to the clockwise light and counterclockwise light at a certain frequency, and the signal detected by the light receiver 6 is set to the phase modulation frequency and its harmonic components.

In addition, the synchronous detection circuit 8 of the signal processing circuit 12 extracts a phase modulation frequency component S1 (1st order), a 2nd harmonic component S2 (2
blow component) The 14th harmonic component S4 (four blow components) is synchronously detected.

However, the way the angular velocity is calculated in CPU10 is different from the conventional method. In other words, instead of using the phase modulation degree (the degree of phase bias given to the left and right beams) which is set in advance as a constant as in the past, the phase modulation degree is calculated from the output of the harmonic signal with respect to the phase modulation frequency. is calculated, and the angular velocity is calculated by using the obtained phase modulation degree. As a result, there is no need for control such as adjusting the degree of modulation of the phase modulator 4 so as to keep the ratio of the fourth harmonic component S4 and the second harmonic component S2 constant, for example.

The details will be explained below.

In the case of the phase modulation method, the signal L' detected by the light receiver 6.

is the clockwise light output of sensing loop 5 p cw,
If the output of counterclockwise light is Pccw, Po ”PCW
+ Pccw + 2 (Paw HPCCW)”
2Jθ(II)cos static (DC component)-4(PCw-P
ccv ) ”” Jl(n's f n quiet cos (
ω. (t-τ/2) (fundamental wave component) -4(Pcw-Pccw)" J2(Il)cosΔ
φcosL2ω. (-τ/2) (second harmonic number) 4 (Pcw-Pccw) ” J3 (1115i
nΔφC05(3ω.(-τ/2)(third harmonic number)...(1) JN in the above equation (1) is a Bessel function.

Δφ is the phase difference due to the Sagnac effect, ω. The modulation frequency 9m is a value corresponding to the phase modulation degree.

The synchronously detected fundamental wave component, the second. The fourth harmonic reduction components are respectively S1, S2. S4, then S1= (Pcw-P
ccw)”” J 1[n)s i nΔφ・(2)S
2= (pcw-PCCW)"' J2(II)co
sΔφ...(3)S4= (Pcw-Pccw)"
” J4(lx)cosΔφ・(4).

On the other hand, the angular velocity ω is determined using the phase difference Δφ due to the Sagnac effect, and a is determined by the scale factor constant, so from equations (2) to (5), a
Jl(i) S2...(6)

Arguments m and i of Bessel function or ratio J of Bessel function
To find the value of (II)/J 1(i), the ratio of the 4th harmonic subtractive component S4 and the 2nd harmonic subject component S2 can be measured, so from the following equation, S4 /S2・J 4(1 )/J2(1)
...(7) J 4 (1) / J 2 (n) and J
2 (1)/J 1 (11), or Jl(n)/
All you have to do is find the relationship with J2(m).

FIG. 2 shows the relationship between the Bessel functions of the first kind.

From the relationship shown in Figure 2, the approximation formula for equation (6) above (accuracy ≦0.5
%) was created, incorporated into the CPU 10 of the optical rotation angular velocity sensor, and evaluated. The results are shown in FIGS. 3 and 4.

Figure 3 shows the optical rotation angular velocity sensor manufactured for evaluation with ±0
．． 01. ±0.02. ±0.03. ±0.04('/s
) Figure 4 is a diagram showing the linear performance of the optical rotation angular velocity sensor manufactured for this evaluation. Performance equal to the design value of the accuracy sensor has been obtained.

(1) In the above embodiment, an example using an approximation formula was shown, but the relationship shown in FIG. 2 is stored in the CPU memory, and S4 /S2
If you use a method of searching by the value of , the performance will be further improved.

(2) Search arguments include S6 /S2, S6 /S
A ratio of even harmonic components such as 4 can be used.

[Effects of the Invention] As described above, according to the present invention, there is no need to control the phase modulator, so a dedicated control circuit is not necessary.
Accordingly, the circuit scale is smaller and cheaper, and assembly becomes easier and reliability is improved. Furthermore, since the angular velocity is calculated using the phase modulation degree obtained by calculation, the reliability of the measurement data is improved.

[Brief explanation of the drawing]

Figure 1 does not show the configuration of the optical rotation angular velocity sensor, Figure 2 shows the relationship between Bessel functions of the first kind, and Figure 3 shows the input of angular velocity to the optical rotation angular velocity sensor manufactured for evaluation of the present invention. FIG. 4 is a diagram showing the linear performance of the optical rotation angular velocity sensor manufactured for evaluation of the present invention. In the figure, 1 is a laser light source, 2a and 2b are optical couplers, 3 is a polarizer, 4 is a phase modulator, 5 is a sensing loop, 6 is a light receiver, 7 is a preamplifier, 8 is a synchronous detection circuit, and 9 is an A/ D
A converter, 10 a CPU, and 11 an oscillator. Patent Applicant Hitachi Cable, Ltd. Hitachi, Ltd. Representative Patent Attorney Nobuo Kinutani Figure 1 14/J2 Time (minutes) Figure 3 Input angular velocity ('/s) Figure 4

Claims (1)

[Claims] 1. The light from the light source is split by an optical coupler, the split light is shifted in phase by a phase modulator, and guided to a sensing loop, and the left and right lights propagated through the sensing loop are split into an optical coupler. In an optical rotation angular velocity sensor using a phase modulation method, the degree of phase modulation is determined from the output of a harmonic signal with respect to the phase modulation frequency, and the degree of phase modulation obtained is An optical rotation angular velocity sensor characterized in that it is provided with arithmetic means for calculating angular velocity using. 2. The optical rotation angular velocity sensor according to claim 1, wherein the calculation means measures the second harmonic signal and the fourth harmonic signal with respect to the phase modulation frequency, and determines the degree of phase modulation from the ratio thereof. .