A method and system for calibrating a circular grating encoder based on a ring laser gyro

Abstract

The present invention provides a method and system for calibrating a circular grating encoder based on a ring laser gyroscope. The method specifically includes the following steps: S1: Obtain the angular increment measurement value RNi of the ring laser gyroscope and the angular displacement measurement value OMi of the circular grating encoder synchronously measured under the trigger of a synchronization signal, where i = 0, 1, …, N; S2: Taking the angular displacement measurement value OMi of the circular grating encoder as the zero point, calculate the angular displacement value RMj of the ring laser gyroscope, where j = 1, …, n; S3: Calculate the error based on the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyroscope, and establish a measurement model of the circular grating encoder according to the error calculation result.

Description

Technical Field

[0001] The present invention relates to the technical field of measurement and control, and particularly relates to a method for calibrating a circular grating encoder based on a ring laser gyroscope. Background Art

[0002] A turntable is a rotating platform whose rotation parameters can change according to specific rules and has high stability. The turntable is applied to the calibration of the angular displacement, angular velocity, angular acceleration and dynamic characteristics of inertial devices, tests the performance of inertial navigation systems and gives a quantitative evaluation. Therefore, to further improve the motion accuracy of the turntable and its calibration accuracy for inertial devices, higher accuracy requirements are put forward for the calibration method of inertial technology test equipment.

[0003] The circular grating encoder is widely used in the measurement of angular motion parameters of the turntable. Its installation and positioning are simple. Applied to the calibration of the turntable, it can be flexibly and conveniently installed on the turntable, with strong operability. The circular grating encoder has good dynamic characteristics and stability, and the measurement accuracy does not change with time. Therefore, the circular grating encoder can be used to measure the angular motion of a uniformly accelerating turntable with high dynamic fast following. However, the circular grating encoder still has measurement system errors caused by non-ideal factors such as installation errors, scale non-uniformity and long-period errors, so that the measurement accuracy is limited.

[0004] Therefore, the existing circular grating encoder has the technical problem of being unable to provide higher-precision measurement in the calibration and dynamic measurement of the turntable. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for calibrating a circular grating encoder based on a ring laser gyroscope. The method mainly identifies the error harmonic model parameters of the circular grating encoder through the measurement results of the ring laser gyroscope, so as to obtain a circular grating encoding measurement model. Through the circular grating encoding measurement model, the technical problem that the circular grating encoder in the related art cannot provide higher-precision measurement in the calibration and dynamic measurement of the rotating device can be solved.

[0006] To solve the above technical problems, the present invention adopts the following scheme:

[0007] A method for calibrating a circular grating encoder based on a ring laser gyroscope, the method specifically includes the following steps:

[0008] S1: Obtain the angular increment measurement value RNi of the ring laser gyroscope and the angular displacement measurement value OMi of the circular grating encoder measured synchronously under the trigger of the synchronization signal, where i = 0, 1,..., N;

[0009] S2: Taking the angular displacement measurement value OMi of the circular grating encoder as the zero point, calculate the angular displacement value RM j of the ring laser gyroscope, where j = 1,..., n;

[0010] S3: Calculate the error based on the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyroscope, and establish a measurement model for the circular grating encoder according to the error calculation result.

[0011] Further, the step S3 specifically includes the following steps:

[0012] S31: Taking the angular displacement RMj of the ring laser gyroscope as a reference, obtain the measurement error vector e through the difference between the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyroscope;

[0013] The measurement error vector e is:

[0014]

[0015] S32: Establish a circular grating encoder error harmonic model for the measurement error of the circular grating encoder over the entire circumference according to the measurement error vector e;

[0016] S33: Obtain the measurement model of the circular grating encoder according to the circular grating encoder error harmonic model.

[0017] Further, the measurement model of the circular grating encoder is: Where, is the measurement value of the circular grating encoder, θ is the true value of the turntable angular displacement, and δ(θ) is the measurement error obtained from the circular grating encoder error harmonic model.

[0018] Further, the circular grating encoder error harmonic model is:

[0019] δ(θ) = A1 cosθ + A2 cos 2θ + … + A m cos mθ + B1 sinθ + … + B m sinmθ +

[0020] C; where, x = [A1, A2, …, A m , B1, …, B m T is the model parameter vector, m is the model order, C is the model parameter, and

[0021] Further, the step S32 includes the following steps:

[0022] S321: Calculate the model order m according to the number of measurement values synchronously measured under the trigger of the synchronization signal;

[0023] ​S322: Calculate the model parameter C of the circular grating encoder measurement model based on the measurement error vector e;

[0024] S323: Calculate the model parameter vector x of the circular grating encoder measurement model through parameter vector calculation based on the model parameter C;

[0025] S324: Establish an error harmonic model of the circular grating encoder based on the model parameter C and the model parameter vector x of the circular grating encoder measurement model.

[0026] Further, in S321, the model order m is: Round down N through the drnd function.

[0027] Further, in S322, the model parameter C is the DC component in the error harmonic model of the circular grating encoder, and is calculated through the measurement error vector e, that is

[0028] Further, in S323, the model parameter vector x is: x = (Q T Q) -1 Q T e';

[0029] Among them, the coefficient matrix Q is: θ j = RM j .

[0030] Further, in S1, the process of obtaining the angular increment measurement value RNi of the ring laser gyroscope and the angular displacement measurement value OMi of the circular grating encoder synchronously measured under the trigger of the synchronization signal is specifically as follows:

[0031] Use the synchronization signal as the trigger signal and send it to the signal acquisition box of the circular grating encoder and the signal acquisition box of the ring laser gyroscope synchronously. When the signal acquisition box of the circular grating encoder and the signal acquisition box of the ring laser gyroscope receive the synchronization signal, record the measurement value of the circular grating encoder and the number of measurement pulses of the ring laser dropout corresponding to the time interval between two adjacent synchronization signals respectively. Use the measurement value of the circular grating encoder as the angular increment measurement value RNi under the current synchronization signal, and use the number of measurement pulses of the ring laser dropout corresponding to the time interval between two adjacent synchronization signals as the angular displacement measurement value OMi of the circular grating encoder under the current synchronization signal.

[0032] A system for calibrating a circular grating encoder based on a ring laser gyroscope, including:

[0033] Synchronization signal trigger measurement module: Obtain the angular increment measurement value RNi of the ring laser gyroscope and the angular displacement measurement value OMi of the circular grating encoder synchronously measured under the trigger of the synchronization signal, where i = 0, 1,..., N;

[0034] Ring laser gyro angular displacement value calculation module: taking the angular displacement measurement value OMi of the circular grating encoder as the zero point, calculating the angular displacement value RMj of the ring laser gyro, where j = 1, …, n;

[0035] Circular grating encoder measurement model establishment module: calculating errors based on the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyro, and establishing a circular grating encoder measurement model according to the error calculation results.

[0036] Advantages of the present invention:

[0037] The present invention provides a method and system for calibrating a circular grating encoder based on a ring laser gyro. The method mainly identifies the error harmonic model parameters of the circular grating encoder through the measurement results of the ring laser gyro, so as to obtain a circular grating encoding measurement model. Through the circular grating encoding measurement model, the technical problem that the circular grating encoder in the related art cannot provide higher-precision measurement in the calibration and dynamic measurement of a rotating device can be solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic flowchart of a method for calibrating a circular grating encoder based on a ring laser gyro in Embodiment 1 of the present invention;

[0039] Figure 2 It is a schematic diagram of the modules of a system for calibrating a circular grating encoder based on a ring laser gyro in Embodiment 1 of the present invention;

[0040] Figure 3 It is the angular increment measurement value RN of the ring laser gyro measured synchronously with the time base signal in Embodiment 1 of the present invention i , the angular displacement measurement value OMi of the circular grating encoder i and the angular displacement value RM of the ring laser gyro j schematic diagram. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of the present invention.

[0042] Unless otherwise specifically stated, the relative arrangements of the components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention.

[0043] At the same time, it should be understood that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationship.

[0044] In addition, for the sake of clarity and conciseness, descriptions of well-known structures, functions, and configurations may be omitted. Those of ordinary skill in the art will recognize that various changes and modifications can be made to the examples described herein without departing from the spirit and scope of the present disclosure.

[0045] Techniques, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be regarded as part of the authorization specification.

[0046] In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0047] The present invention will be described in detail below by referring to the accompanying drawings and in conjunction with embodiments:

[0048] Embodiment 1

[0049] As Figure 1 shown, a method for calibrating a circular grating encoder based on a ring laser gyroscope, the method specifically includes the following steps:

[0050] S1: Obtain the angular increment measurement value RNi of the ring laser gyroscope and the angular displacement measurement value OMi of the circular grating encoder synchronously measured under the trigger of a synchronization signal, where i = 0, 1,..., N;

[0051] S2: Taking the angular displacement measurement value OMi of the circular grating encoder as the zero point, calculate the angular displacement value RMj of the ring laser gyroscope, where j = 1,..., n;

[0052] S3: Calculate the error based on the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyroscope, and establish a measurement model of the circular grating encoder according to the error calculation result.

[0053] Preferably, the step S3 specifically includes the following steps:

[0054] S31: Taking the angular displacement RMj of the ring laser gyroscope as a reference, obtain the measurement error vector e through the difference between the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyroscope;

[0055] The measurement error vector e is as follows:

[0056]

[0057] S32: Establish a circular grating encoder error harmonic model for the measurement error of the circular grating encoder over the entire circumference according to the measurement error vector e;

[0058] S33: Obtain the circular grating encoder measurement model based on the circular grating encoder error harmonic model.

[0059] Preferably, the circular grating encoder measurement model is: where is the measurement value of the circular grating encoder, θ is the true value of the turntable angular displacement, and δ(θ) is the measurement error obtained from the circular grating encoder error harmonic model.

[0060] Preferably, the circular grating encoder error harmonic model is:

[0061] δ(θ) = A1 cosθ + A2 cos 2θ + … + A m cos mθ + B1 sinθ + … + B m sinmθ +

[0062] C; where x = [A1, A2, …, A m , B1, …, B m T is the model parameter vector, m is the model order, C is the model parameter, and

[0063] Preferably, the following steps are included in step S32:

[0064] S321: Calculate the model order m according to the number of measurement values synchronously measured under the trigger of the synchronization signal;

[0065] S322: Calculate the model parameter C of the circular grating encoder measurement model according to the measurement error vector e;

[0066] S3-23: Calculate the model parameter vector x of the circular grating encoder measurement model through parameter vector calculation based on the model parameter C;

[0067] S324: Establish a circular grating encoder error harmonic model according to the model parameter C and the model parameter vector x of the circular grating encoder measurement model.

[0068] Preferably, in S321, the model order m is: Round down N through the drnd function.

[0069] ​Preferably, in S322, the model parameter C is the DC component in the circular grating encoder error harmonic model, which is calculated by measuring the error vector e, that is

[0070] Preferably, in S323, the model parameter vector x is: x = (Q T Q) -1 Q T e′;

[0071] wherein, the coefficient matrix Q is: θ j = RM j .

[0072] Preferably, in S1, the process of obtaining the angular increment measurement value RNi of the ring laser gyroscope and the angular displacement measurement value OMi of the circular grating encoder synchronously measured under the trigger of the synchronization signal is specifically as follows:

[0073] The synchronization signal is used as the trigger signal and sent to the circular grating encoder signal acquisition box and the ring laser gyroscope signal acquisition box synchronously. When the circular grating encoder signal acquisition box and the ring laser gyroscope signal acquisition box receive the synchronization signal, the measurement value of the circular grating encoder and the number of measurement pulses of the ring laser gyroscope corresponding to the time interval between two adjacent synchronization signals are respectively recorded. The measurement value of the circular grating encoder is used as the angular increment measurement value RNi under the current synchronization signal, and the number of measurement pulses of the ring laser gyroscope corresponding to the time interval between two adjacent synchronization signals is used as the angular displacement measurement value OMi of the circular grating encoder under the current synchronization signal.

[0074] Based on the above principle, the present invention is further elaborated:

[0075] In order to solve the technical problem that the existing circular grating encoder cannot provide higher-precision measurement in the calibration and dynamic measurement of the turntable, the present invention provides a method and system for calibrating a circular grating encoder based on a ring laser gyroscope. The method mainly identifies the error harmonic model parameters of the circular grating encoder through the measurement results of the ring laser gyroscope, so as to obtain a circular grating encoding measurement model, and a higher-precision measurement value can be provided through the circular grating encoding measurement model.

[0076] At present, both the ring laser gyroscope and the circular grating encoder are used for measuring the angular motion parameters of the turntable. The circular grating encoder measures the angular motion of a uniformly accelerating turntable with high dynamic and fast following. However, the circular grating encoder still has measurement system errors caused by non-ideal factors such as installation errors, scale non-uniformity, and long-period errors, so that the measurement accuracy is limited.

[0077] Therefore, the present invention selects to use a ring laser gyroscope and a circular grating encoder for synchronous measurement. Specifically, the method of the synchronous measurement is to use a time base signal generator as the synchronous signal output source, and then divide the output synchronous signal into two paths as trigger signals. One path is directly input to the signal acquisition box of the ring laser gyroscope; the other path is input to the signal acquisition box of the circular grating encoder. The signal acquisition box of the circular grating encoder and the signal acquisition box of the ring laser gyroscope respectively save the measurement results of the circular grating encoder and the ring laser gyroscope based on the synchronous signal, and transmit them to the computer through Ethernet, as Figure 2 shown.

[0078] Under the triggering of the above synchronous signal, the measurement results of the circular grating encoder and the ring laser gyroscope can be obtained respectively. Then, in this embodiment, the synchronous measurement of the circular grating encoder and the ring laser gyroscope can be used for a turntable rotating at a constant speed by using the time base signal.

[0079] In this embodiment, in order to enable the circular grating encoder to provide a higher-precision measurement in the calibration and dynamic measurement of the turntable, the present invention establishes a measurement model for the circular grating encoder;

[0080] Specifically, the measurement model of the circular grating encoder is as follows:

[0081] Among them, is the measured value of the circular grating encoder, θ is the true value of the angular displacement of the turntable, and δ(θ) is the measurement error. It can be seen that the present invention takes the sum of the true value θ of the angular displacement of the turntable and the measurement error δ(θ) as the current measured value of the circular grating encoder which can enable the circular grating encoder to provide a higher-precision measured value in the calibration and dynamic measurement of the turntable.

[0082] Moreover, considering the error causes of the circular grating encoder, a harmonic model of the circular grating encoder error is established for the circular grating encoder. The measurement error is obtained through the harmonic model of the circular grating encoder error, and then the measured value of the circular grating encoder can be obtained through the true value of the angular displacement of the current turntable, ensuring that the circular grating encoder has a higher-precision measured value in the calibration and dynamic measurement of the turntable.

[0083] Since the circular grating encoder measures rotational motion, its measurement error is periodic with the rotation angle. And considering that the actual model order is finite, therefore, a harmonic model of the circular grating encoder error can be established for the measurement error of the circular grating encoder over the entire circumference;

[0084] Specifically, the harmonic model of the circular grating encoder error is: δ(θ) = A1 cosθ + A2 cos 2θ + … + A m cos mθ + B1 sinθ + … + Bm sin mθ + C;

[0085] where x = [A1, A2, …, A m , B1, …, B m T is the model parameter vector, m is the model order, C is the model parameter, and the expression of the model parameter C can be obtained from the circular closure principle as:

[0086] For the above-mentioned circular grating encoder error harmonic model, the present invention mainly identifies the model parameters of the circular grating encoder error harmonic model through the measurement results of the ring laser gyroscope, so that the measurement error of the current circular grating encoder can be obtained through the circular grating encoder error harmonic model, and the measurement error can meet the requirement of providing higher-precision measurement for the circular grating encoder.

[0087] In this embodiment, the process of identifying the model parameters of the circular grating encoder error harmonic model through the measurement results of the ring laser gyroscope is specifically as follows:

[0088] First, the circular grating encoder and the ring laser gyroscope need to be synchronized in measurement through the time base signal and measure the uniform turntable. Control the rotating device to rotate at a constant speed, synchronize the measurement data of the ring laser gyroscope and the circular grating encoder with the time base signal, and uniformly obtain N + 1 angular increment measurement values corresponding to adjacent time base signals within one rotation of the rotating device. Denote the angular increment measurement value of the ring laser gyroscope synchronized by the time base signal as RN i , i = 0, 1, …, N, and the angular displacement measurement value of the circular grating encoder as OM i , i = 0, 1, …, N. Calculate the angular displacement RM measured by the ring laser gyroscope with the angular displacement measurement value OM0 of the circular grating encoder as the zero point j , j = 1, …, N;

[0089] Then, taking the angular displacement RM measured by the ring laser gyroscope j as the reference, calculate the measurement error vector of the circular grating encoder. The measurement error vector e is:

[0090] And, since the model parameter C in the circular grating encoder error harmonic model is the DC component in the circular grating encoder error harmonic model, the model parameter C can be calculated through the measurement error vector e, specifically as:

[0091] And the model order m in the circular grating encoder error harmonic model is: The drnd function represents rounding down;

[0092] ​Then, identify the model parameters using the average measurement error after removing the DC component, that is, solve the linear equations Qx = e - C, where the coefficient matrix Q is:

[0093] In the formula, θ j = RM j .

[0094] The solved model parameter vector x is

[0095] x = (Q T Q) -1 Q T e′

[0096] Then, substitute the model parameter vector x and the model parameter C into the error harmonic model of the circular grating encoder to obtain the measurement model of the circular grating encoder after parameter calculation. Through this measurement model of the circular grating encoder, higher-precision measurement values provided by the circular grating encoder in the calibration and dynamic measurement of the turntable can be obtained.

[0097] Specifically, in actual operation, control the turntable to rotate at a constant angular rate of 30° / s, set the frequency of the TTL time base signal output by the signal generator to 10 Hz, record the measurement value of the circular grating encoder when the time base signal arrives, and the number of measurement pulses of the ring laser gyro corresponding to the time interval between two adjacent time base signals, as Figure 3 shown, and calculate the parameters in the error harmonic model according to the obtained measurement data step by step. Substituting the data, the model order m = 6 can be obtained, and the solved parameters are A1 = 0.089869, A2 = -0.111522, A3 = -0.083727, A4 = 0.026135, A5 = 0.021046, A6 = -0.094738, B1 = -0.028333, B2 = 0.088542, B3 = -0.032653, B4 = 0.055007, B5 = -0.054948, B6 = 0.077580, C = 0.190179.

[0098] In summary, the present invention aims at the problem of insufficient accuracy in the application of the existing circular grating encoder in the measurement and calibration of the turntable, and proposes a method for calibrating the circular grating encoder based on the ring laser gyro. The technical key points of this calibration method are: using the ring laser gyro to identify the parameters in the harmonic model established based on the measurement error of the circular grating encoder, separating the measurement system errors caused by non-ideal factors such as the installation error, scale non-uniformity, and long-period error of the circular grating encoder, and improving the measurement accuracy of the circular grating encoder by compensating for this error. The present invention can be applied to the precise measurement and calibration of the dynamic motion parameters of the turntable.

[0099] Embodiment 2

[0100] A system for calibrating a circular grating encoder based on a ring laser gyroscope, comprising:

[0101] A synchronous signal triggered measurement module: obtaining the angular increment measurement value RNi of the ring laser gyroscope and the angular displacement measurement value OMi of the circular grating encoder measured synchronously under the trigger of the synchronous signal, where i = 0, 1, …, N;

[0102] A ring laser gyroscope angular displacement value calculation module: taking the angular displacement measurement value OMi of the circular grating encoder as the zero point, calculating the angular displacement value RMj of the ring laser gyroscope, where j = 1, …, n;

[0103] A circular grating encoder measurement model establishment module: calculating errors based on the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyroscope, and establishing a circular grating encoder measurement model according to the error calculation results.

[0104] As described above, it is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. Based on the technical essence of the present invention, any simple modifications, equivalent replacements, and improvements made to the above embodiments within the spirit and principles of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for calibrating a circular grating encoder based on a ring laser gyroscope, characterized in that, The method specifically includes the following steps: S1: Obtain the angular increment measurement value RNi of the ring laser gyroscope and the angular displacement measurement value OMi of the circular grating encoder synchronously measured under the trigger of the synchronization signal, where i = 0, 1, …, N; S2: Taking the angular displacement measurement value OMi of the circular grating encoder as the zero point, calculate the angular displacement value RMj of the ring laser gyroscope, where j = 1, …, n; S3: Calculate the error based on the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyroscope, and establish a measurement model of the circular grating encoder according to the error calculation result; The specific steps in step S3 include the following steps: S31: Taking the angular displacement RMj of the ring laser gyroscope as the reference, obtain the measurement error vector e through the difference between the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyroscope; The measurement error vector e is: ； S32: Establish a circular grating encoder error harmonic model for the measurement error of the circular grating encoder over the entire circumference according to the measurement error vector e; S33: Obtain the measurement model of the circular grating encoder according to the circular grating encoder error harmonic model.

2. A method for calibrating a circular grating encoder based on a ring laser gyroscope according to claim 1, characterized in that The measurement model of the circular grating encoder is as follows: , where is the measured value of the circular grating encoder, is the true value of the turntable angular displacement, is the measurement error obtained from the circular grating encoder error harmonic model.

3. A method for calibrating a circular grating encoder based on a ring laser gyro according to claim 2, characterized in that, The circular grating encoder error harmonic model is: ; among them, is the model parameter vector, is the model order, C is the model parameter, and .

4. A method for calibrating a circular grating encoder based on a ring laser gyro according to claim 3, characterized in that, The steps in step S32 include the following steps: S321: Calculate the model order m according to the number of measurement values synchronously measured under the trigger of the synchronization signal; S322: Calculate the model parameter C of the circular grating encoder measurement model according to the measurement error vector e; S323: Calculate the model parameter vector x of the circular grating encoder measurement model through parameter vector calculation according to the model parameter C; S324: Establish a circular grating encoder error harmonic model according to the model parameter C and the model parameter vector x of the circular grating encoder measurement model.

5. A method for calibrating a circular grating encoder based on a ring laser gyro according to claim 4, characterized in that In S321, the model order m is as follows: , and N is rounded down by the drnd function.

6. A method for calibrating a circular grating encoder based on a ring laser gyro according to claim 4, characterized in that In S322, the model parameter C is the DC component in the circular grating encoder error harmonic model, which is calculated by measuring the error vector e, that is .

7. A method for calibrating a circular grating encoder based on a ring laser gyroscope according to claim 4, characterized in that, In S323, the model parameter vector x is as follows: ; Among them, the coefficient matrix is as follows: , .

8. A method for calibrating a circular grating encoder based on a ring laser gyroscope according to claim 1, characterized in that, In S1, the process of obtaining the angular increment measurement value RNi of the ring laser gyroscope and the angular displacement measurement value OMi of the circular grating encoder synchronously measured under the trigger of the synchronization signal is specifically as follows: Send the synchronization signal as the trigger signal to the circular grating encoder signal acquisition box and the ring laser gyroscope signal acquisition box synchronously. When the circular grating encoder signal acquisition box and the ring laser gyroscope signal acquisition box receive the synchronization signal, record the measurement value of the circular grating encoder and the number of measurement pulses of the ring laser dropout corresponding to the time interval between two adjacent synchronization signals respectively. Take the measurement value of the circular grating encoder as the angular increment measurement value RNi under the current synchronization signal, and take the number of measurement pulses of the ring laser dropout corresponding to the time interval between two adjacent synchronization signals as the angular displacement measurement value OMi of the circular grating encoder under the current synchronization signal.

9. A system for calibrating a circular grating encoder based on a ring laser gyro, characterized in that, Including: Synchronization signal trigger measurement module: Obtain the angular increment measurement value RNi of the ring laser gyroscope and the angular displacement measurement value OMi of the circular grating encoder synchronously measured under the trigger of the synchronization signal, where i = 0, 1, …, N; Ring laser gyroscope angular displacement value calculation module: Taking the angular displacement measurement value OMi of the circular grating encoder as the zero point, calculate the angular displacement value RMj of the ring laser gyroscope, where j = 1, …, n; Circular Grating Encoder Measurement Model Establishment Module: Calculate the error based on the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyroscope, and establish a measurement model for the circular grating encoder according to the error calculation result. The specific process is as follows: Taking the angular displacement RMj of the ring laser gyroscope as a reference, obtain the measurement error vector e through the difference between the angular displacement measurement value OMi of the circular grating encoder and the angular displacement value RMj of the ring laser gyroscope; The measurement error vector e is: ； Establish a circular grating encoder error harmonic model for the measurement error of the circular grating encoder over the entire circumference according to the measurement error vector e; Obtain the circular grating encoder measurement model according to the circular grating encoder error harmonic model.

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