A method for compensating dynamic error of optical comb inter-mode beat frequency measurement based on acceleration estimation

Abstract

The application belongs to the technical field of laser ranging, and provides a comb inter-mode beat ranging dynamic error compensation method based on acceleration estimation. Firstly, based on the digital quadrature phase-locked phase measurement principle, the comb inter-mode beat dynamic phase measurement error model is established. Then, taking acceleration as a key parameter, the relationship model between the ranging dynamic error and the dynamic target motion parameters is established. Finally, through the estimation of acceleration, the ranging dynamic error compensation model is established, and the dynamic error compensation is realized. The comb inter-mode beat ranging dynamic error can be reduced to micrometer level, and the precision of the laser absolute distance measurement is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of laser ranging technology, specifically relating to a dynamic error compensation method for inter-mode ranging based on acceleration prediction. Background Technology

[0002] Optical comb inter-mode beat ranging technology utilizes multi-order inter-mode beat signals generated by an optical comb as a measuring scale, enabling absolute distance measurements of varying precision. It is currently used internationally in inter-satellite ranging research. The optical comb can directly trace ranging results back to the definition of a meter, showing significant potential for improving accuracy.

[0003] However, when facing dynamic targets, the ranging signal introduces dynamic phase, leading to dynamic errors in phase measurement and causing ranging dynamic errors on the order of hundreds of μm or more. Addressing these limitations, compensating for dynamic ranging errors is a key issue in further improving the accuracy of inter-mode beep ranging technology. Currently, there is limited research by domestic and international experts and scholars on dynamic targets in inter-mode beep ranging. Existing technologies include: 1. Existing technology achieves real-time interchange and synchronous detection of the measurement signal comb and the local oscillation comb by rationally controlling the polarization combining and splitting of two optical combs. Using this scheme, when a moving target passes through a 3-4 times measurement blind zone of the NAR at 15 mm / s, the standard deviation of the residual distance is 1.48 μm. However, the dynamic verification of this research is currently limited to lower translation stage movement speeds, and experimental support is still lacking for the Doppler frequency shift effect and its compensation mechanism under higher dynamic environments.

[0004] 2. Some scholars have analyzed the impact of time jitter and intensity noise on ranging accuracy in dual-comb ranging based on theoretical simulations. They accurately described the dynamic variation of ranging accuracy with distance using noise power spectral density characteristics and analyzed the dynamic ranging capability of dual-combs. Linear optical sampling is performed using two femtosecond laser frequency combs with a small repetition frequency difference. The sub-microsecond interference signal time width is used to approximate the uniform motion of the target, and a proportional ranging algorithm is employed for calculation. Ultimately, a ranging accuracy better than 100 μm and a data refresh rate of 1 kHz are achieved within a 400 m range. Theoretically, high-precision dynamic measurement can be achieved at a maximum relative speed of 19.5 m / s. However, this scheme cannot measure variable-speed motion, and due to the massive data volume, the real-time processing capability places extremely high demands on the performance of the back-end signal processing module. Furthermore, the system requires the simultaneous operation of two precision frequency combs and relies on an onboard atomic clock for repetition frequency locking, resulting in high system complexity and hardware cost.

[0005] 3. Existing technologies include optimal state estimation algorithms based on discrete Kalman filtering. These algorithms establish a three-dimensional dynamic state-space model with position, velocity, and acceleration as elements, and use the five basic iterative equations of Kalman filtering for prediction and updating. At each sampling time, the original ranging data containing Gaussian white noise is recursively processed to obtain the optimal state estimate of the target distance. Ultimately, this achieves a velocity standard deviation of approximately 4 μm / s when the target is moving at a constant speed. However, this method suffers from dynamic response lag; when the target's motion state changes abruptly, the optimal velocity estimate requires a 1-2 s stabilization process to reach an accurate value. Furthermore, some initial parameters in the Kalman filtering algorithm are subjectively given based on empirical values, which may affect the filter's universality and convergence speed in different application scenarios. In addition, the core algorithm relies on five complex matrix recursive iterative equations for real-time computation, placing extremely high demands on the real-time signal processing capabilities of the backend hardware and introducing significant computational and system complexity.

[0006] In summary, existing dynamic ranging methods based on optical frequency combs have shortcomings such as low speed, inability to measure targets with varying speeds, high system complexity, and poor real-time performance. Furthermore, there is limited research on dynamic targets in inter-modal beat ranging, making a compensation method for dynamic errors in inter-modal beat ranging urgently needed. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a dynamic error compensation method for inter-mode beating ranging based on acceleration prediction, thereby resolving the issues in the prior art. The technical solution adopted by this invention is as follows: A dynamic error compensation method for inter-mode beep ranging based on acceleration prediction of an optical comb includes: Step 1, based on the signal sampling rate and sampling time, construct the first... i The sampling data of the measurement signal and the reference signal of the point are used, and the dynamic change of the initial phase of the ranging signal due to the dynamic target is introduced; Step 2: Perform quadrature phase-locked loop processing and mean low-pass filtering on the sampled data to extract the phase DC component and obtain the mean calculation result of the sampled data; Step 3: Based on the mean calculation results of Step 2, construct a dynamic phase measurement error model; the dynamic phase measurement error model is used to quantify the phase measurement error introduced by the dynamic change of the initial phase of the ranging signal during the sampling time. Step 4: Based on the dynamic phase measurement error model, construct the relationship between the ranging dynamic error and the dynamic target motion parameters, and obtain the ranging dynamic error model; Step 5: By estimating the acceleration of the dynamic target, the final ranging dynamic error estimation result is obtained based on the ranging dynamic error model, thereby achieving error compensation.

[0008] Furthermore, step 1 includes: The sampling rates of the measured signal and the reference signal are denoted as... f S Sampling time is recorded as t S ; The first sampled data of the measured signal and the reference signal i The points are represented as follows: ; Among them, S M (i), S R (i) represent the amplitudes of the measured signal and the reference signal at point i, respectively; φ M , φ R For the measurement signal and reference signal at the sampling time t S Phase value at the inner center time; f IF To measure the frequency of the signal and the reference signal; φ i To measure the signal at the first i The dynamic phase carried by the point data during sampling is the dynamic change introduced by the dynamic target to the initial phase of the ranging signal.

[0009] Furthermore, step 2 includes: After multiplying the sampled data with the orthogonal digital signal, four products are obtained. Then, a mean-low-pass filter is used to calculate the mean of each product to extract the DC term; thus, the mean calculation result of the sampled data is obtained. They are respectively: ; ; ; .

[0010] Furthermore, in step 3, the dynamic phase measurement results error Represented as: ; Among them, dynamic phase φ i It is determined by the dynamic target motion parameters.

[0011] Furthermore, step 4 includes: Acceleration is chosen as the dynamic target motion parameter; the relationship between dynamic phase and acceleration is expressed as: ; in,a Indicates the sampling time t S Acceleration at the inner center moment; f IB The frequency of the ranging signal; n g ρ is the group refractive index of the optical comb; c is the speed of light in vacuum. Dynamic phase measurement error Considering only the acceleration 'a', it can be expressed as: ; Based on the inter-mode ranging model of the optical comb, the dynamic error model for ranging using acceleration is obtained as follows: ; in, l The distance to the target to be measured is denoted as .

[0012] Furthermore, the inter-mode beating distance measurement model of the optical comb is expressed as: ; in, l The distance to the target to be measured. φ y For the light comb y The initial phase of the intermodal beat signal, f r The repetition frequency.

[0013] Furthermore, step 5 includes: Substituting the acceleration estimation results into the ranging dynamic error model, the final ranging dynamic error estimation result is obtained as follows: ; in, For acceleration estimation results; starting from the third ranging result of the inter-comb mode ranging system, the dynamic error of ranging is estimated and compensated.

[0014] Furthermore, the update rate of the optical comb inter-mode ranging system is... f UD At any moment t j The following distance measurement results are l j Then the acceleration estimation result at that moment is: .

[0015] The present invention has the following beneficial effects: This method utilizes a dynamic error compensation model for ranging based on acceleration parameter estimation to reduce the dynamic error of inter-comb mode ranging to the micrometer level, achieving high-precision absolute distance measurement and effectively improving the accuracy of inter-comb mode ranging. Attached Figure Description

[0016] Figure 1 This is a flowchart of the present invention; Figure 2 The distance measurement error after error compensation is compared with that before compensation in this invention. Detailed Implementation

[0017] The following will be described in conjunction with embodiments of the present invention. Figures 1-2 The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0018] Inter-mode beating ranging results mainly rely on the phase difference calculation between the measurement path and the reference path, with digital quadrature phase-locked loop (DLL) being a commonly used phase-locking method. When measuring dynamic targets, the initial phase of the ranging signal will change dynamically. During phase-locking, the signal to be measured needs to be sampled, and a phase measurement result is calculated using the sampled data within a certain sampling time. If the initial phase of the signal to be measured changes dynamically within the sampling time, additional measurement errors, i.e., dynamic phase measurement errors, will be introduced. To compensate for this error, this invention proposes a dynamic error compensation method for inter-mode beating ranging based on acceleration prediction.

[0019] like Figure 1 A dynamic error compensation method for inter-mode beep ranging based on acceleration prediction, comprising: Step 1, based on the signal sampling rate and sampling time, construct the first... i The sampling data of the measurement signal and reference signal at the point are used, and the dynamic change of the initial phase of the ranging signal due to the dynamic target is introduced; optionally, the signal sampling rate is... f S =10 MHz, sampling time t S =10 ms. Therefore, each signal will receive 10 ms. 5 Point sampling data.

[0020] The first sampled data of the measured signal and the reference signal i The points can be represented as: ; Among them, S M (i), S R(i) represent the amplitudes of the measured signal and the reference signal at point i, respectively; φ M , φ R For the measurement signal and reference signal at the sampling time t S Phase value at the inner center time; f IF The frequency of the measurement signal and the reference signal is 500 kHz. φ i To measure the signal at the first i The dynamic phase carried by the point data during sampling is the dynamic change introduced by the dynamic target to the initial phase of the ranging signal.

[0021] Step 2: Perform quadrature phase-locked loop processing and mean low-pass filtering on the sampled data to extract the phase DC component and obtain the first... i The result of calculating the mean of the sampled data; After multiplying the sampled data with the orthogonal digital signal, four products are obtained. The mean of each product is calculated using a mean low-pass filter to extract the DC term, thus obtaining the mean of the sampled data. They are respectively ; ; ; .

[0022] Step 3: Based on the mean calculation results of Step 2, construct a dynamic phase measurement error model; the dynamic phase measurement error model is used to quantify the phase measurement error introduced by the dynamic change of the initial phase of the ranging signal during the sampling time. Dynamic phase measurement results error Represented as: ; In the above dynamic phase measurement error model, dynamic phase φ i Determined by the target's motion parameters, it needs to be combined with relevant motion parameter models to obtain a relationship model between the ranging dynamic error and the dynamic target motion parameters, which is used for subsequent compensation of the ranging dynamic error.

[0023] Step 4: Based on the dynamic phase measurement error model, construct the relationship between the ranging dynamic error and the dynamic target motion parameters, and obtain the ranging dynamic error model; This invention selects acceleration as the motion parameter of the dynamic target. The relationship between dynamic phase and acceleration can be expressed as: ; in, a Indicates the sampling time t S Acceleration at the inner center moment; f IB The frequency of the ranging signal is 1 GHz; n g denoted as the group refractive index of the optical comb; c is the speed of light in vacuum, which is 299,792,458 m / s.

[0024] Therefore, the relationship between phase measurement error and acceleration can be obtained as follows: ; Based on the inter-mode ranging model of the optical comb: ; in, l The distance to the target to be measured. φ y For the light comb y The initial phase of the intermodal beat signal, f r The repetition frequency.

[0025] Finally, the dynamic error model for acceleration ranging is obtained as follows: ; Based on this model, the dynamic error of ranging can be compensated by estimating the acceleration of the dynamic target.

[0026] Step 5: By estimating the acceleration of the dynamic target, the final ranging dynamic error estimation result is obtained based on the ranging dynamic error model, thereby achieving error compensation.

[0027] Assuming the update rate of the ranging system is f UD =1 kHz, at time t j The following distance measurement results are l j Then the acceleration estimation result at that moment is: ; Substituting the results into the dynamic error model for ranging based on acceleration, the final estimated dynamic error for ranging can be obtained as follows: ; According to the above formula, starting from the third ranging result given by the ranging system, the dynamic error of ranging can be estimated and compensated.

[0028] A simulation of the dynamic error model for acceleration ranging was performed, with the initial velocity set to 0 and the acceleration to 10 m / s². 2The target underwent uniform acceleration motion for 100 ms continuously, and the final compensation effect was as follows: Figure 2 As shown, before compensation, the dynamic ranging error exceeded 40 μm, and the root mean square (RMS) of the dynamic ranging error within the first 100 ms was 41.6 μm. After compensation, the RMS was reduced to 0.1 μm. Using this method, the dynamic ranging error was effectively compensated to the micrometer level, effectively improving the accuracy of inter-comb ranging. It should be noted that for ranging systems of different frequencies, this method can compensate for ranging errors and improve accuracy regardless of the update rate; without this method, the accuracy also decreases as the update rate decreases. Therefore, this method has a compensation effect regardless of the update rate.

[0029] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, alterations, alterations, or substitutions made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A dynamic error compensation method for inter-mode beep ranging based on acceleration prediction of an optical comb, characterized in that, include: Step 1, based on the signal sampling rate and sampling time, construct the first... i The sampling data of the measurement signal and the reference signal of the point are used, and the dynamic change of the initial phase of the ranging signal due to the dynamic target is introduced; Step 2: Perform quadrature phase-locked loop processing and mean low-pass filtering on the sampled data to extract the phase DC component and obtain the mean calculation result of the sampled data; Step 3: Based on the mean calculation results of Step 2, construct a dynamic phase measurement error model; the dynamic phase measurement error model is used to quantify the phase measurement error introduced by the dynamic change of the initial phase of the ranging signal during the sampling time. Step 4: Based on the dynamic phase measurement error model, construct the relationship between the ranging dynamic error and the dynamic target motion parameters, and obtain the ranging dynamic error model; Step 5: By estimating the acceleration of the dynamic target, the final ranging dynamic error estimation result is obtained based on the ranging dynamic error model, thereby achieving error compensation; Step 4 includes: Acceleration is chosen as the dynamic target motion parameter; the relationship between dynamic phase and acceleration is expressed as: in, a Indicates the sampling time t S Acceleration at the inner center moment; f IB The frequency of the ranging signal; n g ρ is the group refractive index of the optical comb; c is the speed of light in vacuum. f S This indicates the sampling rate of the measured signal and the reference signal; Dynamic phase measurement error Considering only the acceleration 'a', it can be expressed as: Based on the inter-mode beating ranging model of the optical comb, the dynamic error model for ranging with acceleration a is obtained as follows: in, l The distance to the target to be measured is denoted as .

2. The dynamic error compensation method for inter-mode beep ranging based on acceleration prediction according to claim 1, characterized in that, Step 1 includes: The sampling rates of the measured signal and the reference signal are denoted as... f S Sampling time is recorded as t S ; The first sampled data of the measured signal and the reference signal i The points are represented as follows: Among them, S M (i), S R (i) represent the amplitudes of the measured signal and the reference signal at point i, respectively; , For the measurement signal and reference signal at the sampling time t S Phase value at the inner center time; f IF To measure the frequency of the signal and the reference signal; To measure the signal at the first i The dynamic phase carried by the point data during sampling is the dynamic change introduced by the dynamic target to the initial phase of the ranging signal.

3. The dynamic error compensation method for inter-mode beep ranging based on acceleration prediction according to claim 2, characterized in that, Step 2 includes: After multiplying the sampled data with the orthogonal digital signal, four products are obtained. Then, a mean-low-pass filter is used to calculate the mean of each product to extract the DC term; thus, the mean calculation result of the sampled data is obtained. They are respectively: 。 4. The dynamic error compensation method for inter-mode beep ranging based on acceleration prediction according to claim 3, characterized in that, In step 3, the dynamic phase measurement results error Represented as: Among them, dynamic phase It is determined by the dynamic target motion parameters.

5. The dynamic error compensation method for inter-mode beep ranging based on acceleration prediction according to claim 1, characterized in that, The inter-mode ranging model of the optical comb is represented as follows: in, l The distance to the target to be measured. For the light comb y The initial phase of the intermodal beat signal, f r The repetition frequency.

6. The dynamic error compensation method for inter-mode beep ranging based on acceleration prediction according to claim 1, characterized in that, Step 5 includes: Substituting the acceleration estimation results into the ranging dynamic error model, the final ranging dynamic error estimation result is obtained as follows: in, For acceleration estimation results; starting from the third ranging result of the inter-comb frame ranging system, the dynamic error of ranging is estimated and compensated; f UD The update rate is the inter-comb frame ranging system.

7. The dynamic error compensation method for inter-mode beep ranging based on acceleration prediction according to claim 6, characterized in that, The update rate of the optical comb inter-mode ranging system is f UD At any moment t j The following distance measurement results are l j Then the acceleration estimation result at that moment is: 。

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