KR102286261B1 - Lock-in Zero Ring Laser Gyroscope System, and the Operating Method thereof - Google Patents

Abstract

The present invention relates to a ring laser gyroscope using the Sagnac effect and more specifically, to a lock-in zero ring laser gyroscope system and a method for operating the same. The lock-in zero ring laser gyroscope system wherein an active medium is arranged in a ring resonator so that two laser beams having optical frequencies of ω_cw and ω_ccw are clockwise (cw) and counterclockwise (ccw) are simultaneously generated and a fringe pattern formed by a readout prism is processed by a sampling data from an output signal received in a double cell readout detector. In accordance with the lock-in zero ring laser gyroscope system and the method for operating the same of the present invention, a phase error occurring in lock-in can be eliminated by use of phase wrapping/unwrapping algorithms, and stripping without time delay can be performed with a virtual dither signal (VDS) without a separate pick-off sensor.

Description

Lock-in Zero Ring Laser Gyroscope System, and the Operating Method thereof

The present invention relates to a ring laser gyroscope using the Sagnac effect, and by using a phase wrapping/unwrapping algorithm, a phase error occurring in lock-in is removed, and a separate pick-off sensor A lock-in zero-ring laser gyroscope system and a driving method therefor without time delay by performing stripping as VDS (Virtual Dither Signal) without any technical field.

As a background technology for the present invention, there is a technique for double demodulation of an angular vibration signal of a ring laser gyro of Korean Patent Registration No. 10-1475799 B1 shown in FIG. 1 .

This technology relates to a method for double demodulation of an angular vibration signal of a ring laser gyro that improves the sampling rate of an angular vibration demodulator used to obtain a gyro output signal in a ring laser gyro using a resonator angular vibration method. A method for double demodulation of an angular vibration signal of a ring laser gyro, comprising: an angular vibrator for angular vibration of the ring laser resonator; and a detection sensor for detecting a beat signal generated through the angular vibration. estimating a rising time or a falling time of the cross signal as a period reference time; calculating an angular oscillation period using a time interval between rising points or falling points; calculating a point that is 1/2 of the calculated angular oscillation period and determining the angular oscillation half-cycle time point following the reference time; iteratively estimating a period reference time point and a half-cycle time point; and sampling the ring laser gyro output signal by integrating the beat pulses between the iteratively estimated period reference time points and the half cycle time points.

As another background technology for the present invention, there is a method for compensating a phase error of a ring laser gyroscope of Korean Patent Registration No. 10-1121879 B1 shown in FIG. 2 and an apparatus technology therefor. In this technology, the frequency lock-in of the light oscillating in both directions occurs by reverse scattering that occurs in the reflector of the ring laser gyroscope, and the phase error differential to compensate for the phase error of the gyroscope. It features an Area Integration and Compensation (AIC) method of signal.

US 10-1475799 B1 US 10-121879 B1

Kazuyoshi Itoh, “Analysis of the phase unwrapping algorithm”, “Applied Optics, Vol 21, No. 14 2470, 1982 Dennis C. Ghiglia and Mark D. Pritt, “Two-dimensional Phase Unwrapping ”, Wiley and Sons, 1998 Sin-Woo Song, Jae-Cheul Lee, Suk-Kyo Hong, and Dongkyoung Chwa, “random walk reduction algorithm in ring laser gyroscopes”. 12 (2010) 115501

The present invention eliminates a phase error occurring in lock-in by using a phase lapping/unwrapping algorithm, and also performs stripping as a VDS (Virtual Dither Signal) without a separate pick-off sensor. An object of the present invention is to provide a lock-in zero-ring laser gyroscope system with no time delay and a method for driving the same.

In the present invention, ω _cw and ω _ccw An active medium is placed in the ring resonator so that two laser beams with an optical frequency of A lock-in zero-ring laser gyroscope system and a driving method for signal processing by sampling an output signal received by a readout detector composed of double cells from an interference pattern formed by a readout prism provided as a solution to

The lock-in zero-ring laser gyroscope system and the driving method thereof of the present invention eliminate a phase error occurring in lock-in by using a phase wrapping/unwrapping algorithm, and a separate pick-off sensor (pick-off) There is a technical effect that a time delay does not occur by performing stripping as a VDS (Virtual Dither Signal) without a sensor).

1 is a background art, the configuration of the angular vibration signal double demodulation method of the ring laser gyro
Figure 2 is another background art, the configuration of a method for compensating a phase error of a ring laser gyroscope and a device technology therefor
3 is an example of a ring laser gyroscope configuration
4 is an example of ψ and ψ _err.
Fig. 5 shows the relationship between the phase ψ derived by Sagnac and the wrapped phase Ф;
Figure 6 is an example of the result according to the unwrapping (unwrapping) procedure applied to the ring laser gyroscope of the present invention
7 is an example of direct phase measurement (DPM)
8 is a relationship between a virtual dither signal (VDS) and dither amplitude according to the present invention;
9 is an Allan scatter plot after applying the wrapping/unwrapping algorithm to a ring laser gyroscope with a lock-in threshold of 0.1°/sec.
10 is a configuration of a lock-in zero-ring laser gyroscope system of the present invention;
11 is a flowchart of a driving method of a lock-in zero ring laser gyroscope system;

The following is merely illustrative of the principles of the invention. Accordingly, those of ordinary skill in the art to which this technology pertains, although not explicitly described or shown herein, can implement the principles of the present invention and invent various devices and methods included in the concept and scope of the present invention. . It should be understood that all conditional terms and examples listed herein are, in principle, expressly intended only for the purpose of understanding the inventive concept and are not limited to the specifically enumerated embodiments and states as such. . Moreover, it is to be understood that all detailed description reciting specific embodiments, as well as principles, aspects, and embodiments of the present invention, are intended to include structural and functional equivalents of such matters.

The above objects, features and advantages will become more apparent through the following detailed description in conjunction with the accompanying drawings. In describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 shows an example of a ring laser gyroscope configuration. A ring laser gyroscope (RLG) rotates assuming that the light source rotates at an angular velocity (Ω) when two beams of light travel in opposite directions along a closed path with a constant radius as shown in the figure. It is an inertial sensor using the Sagnac effect, in which light passing in the opposite direction reaches the light source faster than a beam traveling in the rotational direction. At this time, the time difference or phase difference (path difference) between the two lights traveling in opposite directions causes the movement of the fringe pattern, and the magnitude is proportional to the input angular velocity, so rotation input information is provided.

At this time, since the light energy is limited in the path by the precision machined mirror, the reflectance and scattering of the mirror have a significant effect on the ring laser gyroscope performance. When the input angular velocity is very small, back scattering from the mirror interferes with the two counter-rotating waves, making the two frequencies equal. This is called a lock-in phenomenon, and in such a state, the ring laser gyroscope cannot display the output to the input.

The main factors limiting the performance of ring laser gyroscopes are random walk and quantization noise, which determine the alignment time of navigation systems, and bias instability that affects long-term accuracy. (bias instability).

The present invention relates to a ring laser gyroscope system in which a lock-in phenomenon that minimizes quantization noise and quantum limited random walk is eliminated and a driving method thereof. To this end, the present invention provides a ring laser gyroscope system and a driving method thereof that eliminates a phase error occurring in lock-in using a phase wrapping/unwrapping algorithm. In addition, the ring laser gyroscope system and the driving method of the present invention are a ring laser gyroscope system that performs stripping as a VDS (Virtual Dither Signal) without a time delay without a separate pick-off sensor. and a driving method thereof.

3, the ring laser gyroscope has ω _cw and ω _ccw It is a type of heterodyne interferometer equipped with an active medium in a ring resonator so that two laser beams with an optical frequency of clockwise (cw) and counterclockwise (ccw) oscillate. Here, the ring laser gyroscope is a partially transparent mirror (302: partially transparent mirror) and the two output beams formed by a readout prism disposed behind generate an interference pattern (fringe pattern) and it is a readout detector (readout detector) to receive light. The readout detector is a double-cell photodetector, and is used so that the distance between the detection elements is spaced apart by 1/4 of the interval of the interference fringes. The output of the readout detector is provided in the form of sin(ψ) and cos(ψ). Ψ is the difference proportional to the angular rotational speed ω of the light source, Δω = ω _cw - ω _ccw It is represented by a beat signal represented by . In addition, the intensity of the cw and ccw beams is measured with two separate photo detectors mounted on a power channel prism behind a partially transparent mirror (302) to generate signals necessary for resonator path length control, etc.

Such a ring laser gyroscope has limited performance as an inertial sensor due to errors due to scale factor fluctuations, null shifts, and lock-in. Especially. The most limiting factor in the performance of a ring laser gyroscope is the dead zone caused by lock-in, which is caused by backscattering of the mirror.

To overcome the lock-in problem, various biasing techniques are applied, and a dithering technique is a representative technique. This technique sweeps the dead zone by mechanically vibrating a ring laser gyroscope around a sensitive axis using a piezoelectric element or the like. However, if the dither amplitude is constant, it is inappropriate to remove all lock-ins, and sometimes adds amplitude noise to the dither. However, if the noise is not completely randomized, bias drift occurs, and this error is generally the main cause of random walk and random drift that occurs at all turnarounds.

The output of the ring laser gyroscope also contains quantization noise. The output of a ring laser gyroscope, which is sampled periodically as a pulse, at most rotational speeds, there are no integer pulses that fit exactly into that period, so a portion of the pulse is passed on to the next period. The output of a ring laser gyroscope is configured to count pulses continuously, so it loses some of the pulses to maintain accurate angular information, resulting in quantization noise.

The present invention provides a ring laser gyroscope system for removing random walk and quantization noise using a wrapping/unwrapping algorithm and a driving method thereof. In addition, the present invention proposes a DPM (Direct Phase Measurement Scheme) method to obtain a ring laser gyroscope output, and a new Virtual Dither Signal (VDS) method for implementing stripping without a time delay without an external pick-off sensor suggest

Hereinafter, the wrapping/unwrapping algorithm of the present invention will be described.

In sinusoidal dithering, the gyro equation can be constructed as follows.

[Equation 1]

ψ′= 1/K _scf [Ω _ext +Ω _d cos(ω _d t)-Ω _L sin(ψ+ρ)]

= ψ′ _ideal + ψ′ _err

where K _scf = 2π·(λL / 4A) is the scale factor, A is the area surrounded by the laser beam path, L is the cavity length, λ is the wavelength of the laser, Ω _ext is the external angular rate input, Ω _d and ω _d are the dither amplitude and dither frequency, respectively. Ω _L = K _scf ·c/L·E ₀ and ρ represent the lock-in threshold and the phase shift due to back scatter, respectively. Ideally, if there is no backscatter in the mirror, then d(ψ _err )/dt becomes 0. in this case,

[Equation 2]

ψ′ _ideal = 1/K _scf [Ω _ext + Ω _d cos(ω _d t)]

becomes [Equation 1] and [Equation 2] are first-order differential equations, ψ and ψ _{ideal by the fourth-order Runge-Kutta method} can be obtained Therefore, the phase error can be calculated as

[Equation 3]

ψ _err = ψ-ψ _ideal

4 shows an example of _{ψ and ψ err.} Referring to the drawings, it can be seen that at all the switching points of the sine wave dithering, that is, the phase error is generated step by step (zero rate crossing) at the intersection where the rotation angular velocity becomes zero. A loss of phase information occurs in this dithering turn-around. In the figure, δ ₁ , δ ₂ , δ ₃ and δ ₄ are the relative phase jumps at the zero phase crossing point, and ε ₁ , ε ₂ , ε ₃ and ε ₄ are the angles accumulated in the gyro output at the zero phase crossing point due to the phase jump. rotation error. In this case, the relative phase jump may be calculated at each turnaround point and the phase error may be accumulated for compensation. That is, _{we can calculate as ε 1} = δ ₁ , ε ₂ = δ ₂ + δ ₁ and ε ₃ = δ ₃ + δ ₂ + δ _{1 ,} and if the phase error exceeds π, one pulse is added to compensate . In dithered ring laser gyroscopes, these phase errors accumulate at every turnaround and cause random walk or random drift. If there are no lock-in errors, there are no offset and angle errors.

Next, based on the unwrapping algorithm, instead of δ, the continuous phase error ε, i.e. ψ _err How to calculate is described. Two laser beams in a ring laser gyroscope can be expressed as follows.

[Equation 4]

E ₁ = A ₁ e ^{i ( ω1t + θ1 )}

E ₂ = A ₂ e ^{i ( ω2t + θ2 )}

where A ₁ and A ₂ are the amplitudes, ω1 and ω2 are the frequencies, and θ1 and θ2 are the initial phases of the two beams. Assuming that the two amplitudes A ₁ and A ₂ are equal and equal to A, the light intensity I can be expressed as

[Equation 5]

I = Io [1 + cos(Δωt + Δθ)]

where Io = │A│ ² , ω = ω1 - ω2, Δθ = θ1 - θ2.

In this case, the output signal of the read-out detector can be expressed as follows.

[Equation 6]

i _PD1 = a ₀ + a ₁ sin(ψ + ψ ₀ )

i _PD2 = b ₀ + b ₁ cos(ψ)

where ψ = Δωt + Δθ, and to simplify the expression, assuming that a ₀ = b ₀ = 0, a ₁ = b ₁ = 1, ψ ₀ = 0, and taking the phase extraction operation of the arc tangent of the two arguments, It becomes like this:

[Equation 7]

Ф = atan2[(sin(ψ), cos(ψ)]

arctan2 is the quadrant arc tangent, known as the wrapping operator, where -π <Ф(t)<π.

Fig. 5 shows the relationship between the phase ψ derived by Sagnac and the wrapped phase Ф. Here, the wrapped phase Ф is a physical quantity that can be measured from the output signal of the read-out detector of Equation 6 above.

In the gyro equation of [Equation 1], the phase error ψ _err due to lock-in is as follows;

[Equation 8]

ψ _err = ∫ψ′ _err dt = -1/Kscf·Ω _L ∫sin(ψ+ρ)dt

= -1/Kscf·Ω _L ∫sin(Ф+ρ)dt

, and the phase error ψ _err for N samples spaced Δt is,

ψ′_err(i) Δt = -1/K_scfㆍΩ_Lㆍ

sin{ψ(i)+ρ}Δt ψ _err =

ψ′ _err (i) Δt = -1/K _scf ㆍΩ _L ㆍ

sin{ψ(i)+ρ}Δt

sin{Ф(i)+ρ}Δt= -1/K _scf ㆍΩ _L dot

sin{Ф(i)+ρ}Δt

can be saved with

Since the unwrapped phase ψ is (2πn+Ф), the wrapped phase Ф can be _{integrated from t=0 to t 0} and used to calculate the phase error ψ _err (t). Lock-in threshold Ω _L and the phase shift ρ due to back scatter is a physical quantity that is measured in advance and is almost constant when using a high-quality mirror. In addition, in order to increase the accuracy, it is also possible to define a coupling function C for measurement.

The wrapping algorithm requires only heterodyne sampling to obtain the wrapped phase Ф in [Equation 7]. This eliminates the need for zero-crossing time measurements of SIN/COS signals using a high-frequency clock.

Next, a phase unwrapping algorithm for extracting the actual phase ψ will be described. The unwrapping algorithm of the present invention can calculate the unwrapped phase by integrating the wrapped phase difference as follows.

Step 1 - Calculate the phase difference from [Equation 7],

[Equation 9]

D(i) = Ф(i+1)-Ф(i), i = 1,… , N-1

Step 2 - After calculating the wrapped phase difference,

[Equation 10]

Δ(i) = arctan2 {sin D(i), cos D(i)}, i = 1,… , N-1

Step 3 - Unwrapping by summing the wrapped phase differences.

[Equation 11]

ψ(i) = ψ(i-1) + Δ(i-1), i = 2,… N

where ψ(1) = Ф(1)

6 shows the results according to the unwrapping procedure applied to the ring laser gyroscope of the present invention. Fig. 6(a) shows the output SIN(ψ) and COS(ψ) of the ring laser gyroscope, and (b) shows the result of the ATAN wrapping operation. When the SIN waveform changes from -1 to 1, the wrapped phase passes through zero, a jump from π to π occurs, and vice versa. Figure (c) shows the difference between adjacent sampling points generating pulses with amplitudes of π or -π. In the figure of (c), when the phase increases or vice versa, the sign becomes negative. In addition, since it can be seen that Δ(i) in Equation 10 described above allows dither motion without time delay, it is possible to provide a reference signal for dither stripping as the virtual dither signal (VDS). can Fig. 6(d) shows the unwrapped phase, which shows that the original phase ψ can be fully recovered.

Next, the process of directly extracting the phase will be described.

In [Equation 3] and [Equation 11], the ideal phase ψ _ideal can be obtained by removing the phase error.

[Equation 12]

ψ _ideal = ψ-ψ _err

This is the basis of the lock-in zero ring laser gyroscope (LZG), which completely eliminates the phase error resulting from the lock-in of a dithered ring laser gyroscope.

And the phase by the external rotation input can be obtained as follows.

[Equation 13]

ψ _ext = ψ _ideal -ψ _dither

Here, the phase due to the dither operation can be calculated by directly integrating.

[Equation 14]

ψ _dither = ∫ψ′ _dither dt

= (1/K _scf )ㆍ(Ω _d /ω _d )ㆍsin(ω _d t)

From the previous [Equation 1], the phase by the external rotation input can be obtained as follows.

[Equation 15]

ψ _ext = 1/K _scf ㆍ∫Ω _ext dt

Therefore, the input rotation rate and the external angular rate input are calculated as follows.

[Equation 16]

Δψ _ext = ψ′ _ext ㆍΔt = Ω _ext /K _scf ㆍΔt

[Equation 17]

Ω _ext = K _scf ㆍΔψ _ext /Δt

Here, the data rate and the processing rate 1/Δt are determined by the angle and the frequency of translational motion received by the navigation system to which the ring laser gyroscope system of the present invention is applied. This method will be referred to as direct phase measurement (DPM). For example, the DPM result at 2400Hz for the Earth's rotational speed is estimated to be 0.002471°/sec, that is, 8.896°/hr at the local latitude as shown in FIG. 7 . Therefore, the phase ψ of [Equation 1] described above, the unwrapped phase ψ(i) of [Equation 11], the phase ψ _dither due to the dither operation of [Equation 14], and the external angular velocity input of [Equation 17] The CPU of the processor for calculating Ω _ext requires less than 100 μsec of operation time for a 10 MB data sample, and if data processing is performed in the processor at a cycle of 2.5 KHz (400 μsec), it can sufficiently execute all calculations required for DPM.

Next, dither motion stripping of the present invention will be described. Dither motion stripping generally includes a dither stripping/trapping technique and a dither suppression technique by digital filtering. In dither stripping/trapping technology, an inductive piezoelectric sensor is used to detect dither motion of a ring laser gyroscope block relative to the case. However, this kind of dither pick-off sensor has hysteresis, linearity, stability and repeatability errors, which can limit the accuracy of the dither motion and consequently degrade the gyro accuracy. To solve this, the amplitude and phase of the ring laser gyroscope and the pick-off sensor must be synchronized, but over time, the dither pick-off signal changes due to the increase in the internal temperature, so there is a problem that must be compensated even with a complex algorithm. Digital filtering technology can use a dithering sensor, but the reflectivity of the filter is not sufficient to suppress the dithering signal, and there is a problem in that a time delay occurs due to processing.

The present invention applies a new dither stripping configuration of VDS based on unwrapping algorithm to overcome this problem. According to the dither stripping configuration of the present invention, an additional dither pick-off sensor is not required, thereby reducing costs, and since there is no time delay, dither removal can be easily and accurately performed.

The dither motion can be described by two parameters: the dither amplitude Ω _d and the dither frequency ω _{d .} As shown in (c) of FIG. 6, Δ(i) represents a dither operation, and as shown in FIG. 10 _{, as it changes linearly according to the dither amplitude Ω d} , a virtual dither signal (VDS: virtual) for removing the dither motion. can be used as a dither signal). The dither amplitude can be calculated as follows by measuring the maximum and/or minimum amplitude of VDS.

[Equation 18]

Ω _d = K·D _max

where D _max is the maximum amplitude of Δ(i).

FIG. 9 shows an Allan scatter plot after applying the wrapping/unwrapping algorithm to a ring laser gyroscope having a lock-in threshold of 0.1 [°/sec] as an embodiment of the present invention. In the embodiment of the figure, the random walk is ^{reduced to about 1×10 −4} °/(hr) ^1/2 and the quantization error is 1×10 ⁻⁴ [°]. This result shows the performance of a locked-in zero-ring laser gyroscope system in which random walk and quantization errors are removed.

Figure 10 shows the configuration of the lock-in zero ring laser gyroscope system of the present invention. The ring laser gyroscope system of the present invention includes a control processor 600 that performs control associated with each module of the ring laser gyroscope system; and ω _cw and ω _ccw An active medium is placed in the ring resonator so that two laser beams with an optical frequency of (302: readout prism (400: readout prism) disposed on the back of (302: partially transparent mirror) readout detector (500: readout detector) consisting of a double cell photodetector that receives the interference pattern (fringe pattern) formed by the One ring laser gyroscope equipped with the read-out detector 500 receives the output current signal for each dual-cell photodetector, adjusts the bias and output gain, and outputs two currents as output voltage signals for each dual-cell photodetector. - voltage amplifier 502; an A/D converter 504 for sampling the output voltages of the two current-voltage amplifiers 502, respectively; a wrapping phase extraction module 506 for performing a phase extraction operation of a quadrant arc tangent from the sampled dual-cell photodetector-specific output data; a phase error calculation module 508 for calculating a phase error _{ψ err} due to lock-in in the gyro equation; a phase difference extraction module 510 receiving the output of the phase error calculation module 508 and extracting a phase difference D(i); a wrapping phase difference calculation module 512 that calculates the wrapped phase difference Δ(i) from the output of the phase difference extraction module 510 and provides it as a virtual dither signal (VDS) for removing dither motion; an unwrapping module 514 summing the wrapped phase differences from the output of the wrapping phase difference calculation module 512 to provide an unwrapped output ψ(i); Unwrapping output ψ ψ to calculate an ideal phase ψ _ideal to remove phase errors from (i) _ideal arithmetic module 516; _{a ψ dither} calculation module 518 that receives a virtual dither signal (VDS) of the lapping phase difference calculation module 512 and calculates a _{phase ψ dither due to a dither operation;} Ψ _ideal for calculating the phase ψ _ideal due to external rotation input from the _dither phase ψ phase extraction module 520; ψ _ideal An external angular velocity input from the output of the phase extraction module (520) (external input angular rate) for computing Ω Ω _{ext ext} calculation module 522; _{Ω ext} that outputs the calculated external angular rate input _{Ω ext} It is composed of an output unit 524 .

11 is a flowchart of a method of driving a lock-in zero ring laser gyroscope system of the present invention. The driving method of the lock-in zero ring laser gyroscope system of the present invention of the present invention,

- S100: starting the operation of the ring laser gyroscope system;

- S110: ring laser gyroscope; and the output current signal for each double cell photodetector of the read-out detector 500;

i _PD1 = a ₀ + a ₁ sin(ψ + ψ ₀ )

i _PD2 = b ₀ + b ₁ cos(ψ)

The two current-voltage amplifiers 502 each sample the output voltages of the two current-voltage amplifiers,

v _PD1 = sin(ψ(i)) ; i=1,...,N

v _PD2 = cos(ψ(i)) ; i=1,...,N

sampling with ;

- S120: extracting the phase Ф = atan2[(sin(ψ), cos(ψ)] of the quadrant arc tangent from the sampled output data for each double cell photodetector;

- S130: phase error due to lock-in in the gyro equation,

ψ′_err(i) Δt = -1/K_scfㆍΩ_Lㆍ

sin{ψ(i)+ρ}Δt ψ _err =

ψ′ _err (i) Δt = -1/K _scf ㆍΩ _L ㆍ

sin{ψ(i)+ρ}Δt

sin{Ф(i)+ρ}Δt= -1/K _scf ㆍΩ _L dot

sin{Ф(i)+ρ}Δt

calculating ;

- S140: Phase difference D(i) = Ф(i+1)-Ф(i), i = 1, ... from the phase Ф of the quadrant arc tangent calculated in step S 120 above. , calculating N-1;

- S150: phase difference wrapped from phase difference D(i),

Δ(i) = arctan2 {sin D(i), cos D(i)}, i = 1,… , N-1

generating a virtual dither signal (VDS) by calculating

- S160: after calculating the wrapped phase difference Δi, summing the wrapped phase difference and unwrapping to calculate ψ(i)

ψ(i) = ψ(i-1) + Δ(i-1), i = 2,… N

where ψ(1) = Ф(1);

- S170: calculating an _{ideal phase ψ ideal} by removing a phase error from _{ψ ideal} = ψ-ψ _err;

- S180 : Δi = arctan2 {sin D(i), cos D(i)}, i = 1,… , N-1

Ω _d = K·D _max using

phase due to the dither operation of the virtual dither signal (VDS),

ψ _dither = ∫ψ′ _dither dt = (1/K _scf )ㆍ(Ω _d /ω _d )ㆍsin(ω _d t)

calculating ;

- S190: calculating a phase by an external rotation input using a function of _{ψ ext} = ψ _{ideal - ψ dither;}

- S200 : ψ _ext = 1/K _scf ㆍ∫Ω _ext dt, so

From Δψ _ext = ψ′ _ext ㆍΔt = Ω _ext /K _scf ㆍΔt,

external angular rate input

Ω _ext = K _scf ㆍCalculating and outputting _{Δψ ext /Δt;}

is composed of

In the present invention, the ring laser gyroscope system can be continuously driven by repeatedly performing the above step S110 from the previous step S110 after performing the step S200.

According to the ring laser gyroscope system and the driving method of the present invention described as described above, a phase error occurring in lock-in is removed by using a phase lapping/unwrapping algorithm, and a VDS (Virtual Dither Signal) is used for stripping. It is characterized in that there is no time delay by excluding an external pick-off sensor.

Although the ring laser gyroscope system and the driving method of the present invention have been described with reference to the limited embodiments and drawings, the present invention is not limited thereto, and the Of course, various modifications and variations are possible within the scope of the technical spirit of the invention and the scope of the claims to be described below.

100: photo detector 200: power prism
300: mirror 302: partially transmitted mirror
400: readout prism 500: readout detector
502: current-voltage amplifier 504: A/D conversion unit
506: wrapping phase extraction module 508: phase error calculation module
510: phase difference extraction module 512: wrapping phase difference calculation module
514: unwrapping module 516: ψ _ideal arithmetic module
518: ψ _dither output module 520: ψ _ideal Phase extraction module
522 : Ω _ext Output module 524: Ω _ext output
600: control processor

Claims (4)

ω _cw and ω _ccw An active medium is placed in the ring resonator so that two laser beams with an optical frequency of ) to form an interference pattern by two beams by means of a readout detector (500: readout In the lock-in zero ring laser gyroscope system that samples the output signal received by the detector) and processes the signal,

Control processor 600 for performing control associated with each module of the ring laser gyroscope system; and
two current-voltage amplifiers 502 for receiving the output current signal for each dual-cell photodetector of the read-out detector 500, adjusting bias and output gain, and outputting the output voltage signal for each dual-cell photodetector, respectively;
an A/D converter 504 for sampling the output voltages of the two current-voltage amplifiers 502, respectively;
a wrapping phase extraction module 506 for performing a phase extraction operation of a quadrant arc tangent from the sampled dual-cell photodetector-specific output data;
a phase error calculation module 508 for calculating a phase error _{ψ err} due to lock-in in the gyro equation;
a phase difference extraction module 510 receiving the output of the phase error calculation module 508 and extracting a phase difference D(i);
a wrapping phase difference calculation module 512 that calculates the wrapped phase difference Δ(i) from the output of the phase difference extraction module 510 and provides a virtual dither signal (VDS) for removing dither motion;
an unwrapping module 514 summing the wrapped phase differences from the output of the wrapping phase difference calculation module 512 to provide an unwrapped output ψ(i);
Unwrapping output ψ ψ to calculate an ideal phase ψ _ideal to remove phase errors from (i) _ideal arithmetic module 516;
ideal phase ψ _ideal class _{a ψ dither} calculation module 518 that receives a virtual dither signal (VDS) of the lapping phase difference calculation module 512 and calculates a _{phase ψ dither due to a dither operation;}
Ψ _ideal for calculating the phase ψ _ideal due to external rotation input from the _dither phase ψ phase extraction module 520;
ψ _ideal An external angular velocity input from the output of the phase extraction module (520) (external input angular rate) for computing Ω Ω _{ext ext} calculation module 522;
_{Ω ext} output unit 524 _{for outputting Ω ext} that is the calculated external angular rate input;
A lock-in zero-ring laser gyroscope system, characterized in that it consists of.
ω _cw and ω _ccw An active medium is placed in the ring resonator so that two laser beams with an optical frequency of ) forms an interference pattern by two output beams by means of a read-out detector (500: 500: A method of driving a lock-in zero-ring laser gyroscope system for sampling and signal processing an output signal received by a readout detector, the method comprising:

- S100: starting the operation of the ring laser gyroscope system;

- S110: ring laser gyroscope; and the output current signal for each double cell photodetector of the read-out detector 500;
i _PD1 = a ₀ + a ₁ sin(ψ + ψ ₀ )
i _PD2 = b ₀ + b ₁ cos(ψ)
The two current-voltage amplifiers 502 each sample the output voltages of the two current-voltage amplifiers,
v _PD1 = sin(ψ(i)) ; i=1,...,N
v _PD2 = cos(ψ(i)) ; i=1,...,N
sampling with ;

- S120: extracting the phase Ф = atan2[(sin(ψ), cos(ψ)] of the quadrant arc tangent from the sampled output data for each double cell photodetector;

- S130: phase error due to lock-in in the gyro equation,
ψ _err =

ψ′ _err (i) Δt = -1/K _scf ㆍΩ _L ㆍ

sin{ψ(i)+ρ}Δt
= -1/K _scf ㆍΩ _L dot

sin{Ф(i)+ρ}Δt
calculating ;

- S140: Phase difference D(i) = Ф(i+1)-Ф(i), i = 1, ... from the phase Ф of the quadrant arc tangent calculated in step S 120 above. , calculating N-1;

- S150: phase difference wrapped from phase difference D(i),
Δ(i) = arctan2 {sin D(i), cos D(i)}, i = 1,… , N-1
generating a virtual dither signal (VDS) by calculating

- S160: after calculating the wrapped phase difference Δi, summing the wrapped phase difference and unwrapping to calculate ψ(i)
ψ(i) = ψ(i-1) + Δ(i-1), i = 2,… N
where ψ(1) = Ф(1);

- S170: calculating an _{ideal phase ψ ideal} by removing a phase error from _{ψ ideal} = ψ-ψ _err;

- S180 : Δi = arctan2 {sin D(i), cos D(i)}, i = 1,… , N-1
Ω _d = K·D _max using
phase due to the dither operation of the virtual dither signal (VDS),
ψ _dither = ∫ψ′ _dither dt = (1/K _scf )ㆍ(Ω _d /ω _d )ㆍsin(ω _d t)
calculating ;

- S190: calculating a phase by an external rotation input using a function of _{ψ ext} = ψ _{ideal - ψ dither;}

- S200 : ψ _ext = 1/K _scf ㆍ∫Ω _ext dt, so
From Δψ _ext = ψ′ _ext ㆍΔt = Ω _ext /K _scf ㆍΔt,
external angular rate
Ω _ext = K _scf ㆍCalculating and outputting _{Δψ ext /Δt;}

A method of driving a lock-in zero-ring laser gyroscope system, characterized in that consisting of.
The method of claim 2 , wherein the lock-in zero-ring laser gyroscope system is driven.
In the step S200, the input rotation rate (input rotation rate)
Ω _ext = K _scf ㆍCalculate and output _{Δψ ext /Δt,}
A method of driving a lock-in zero-ring laser gyroscope system, characterized in that it is configured to be repeatedly performed from step S110.
The method of claim 2 , wherein the lock-in zero-ring laser gyroscope system is driven.
The phase difference wrapped from the phase difference D(i) in step S150,
Δ(i) = arctan2 {sin D(i), cos D(i)}, i = 1,… , N-1
provides a virtual dither signal (VDS: virtual dither signal) for removing dither motion by calculating
The dither amplitude Ω _d is, when the maximum amplitude of Δ(i) is D _max,
Ω _d = K·D _max
A method of driving a lock-in zero-ring laser gyroscope system, characterized in that determined as

Images